Re: Non-locality and MWI
On 11-05-2016 22:31, John Mikes wrote: BruceK and Smitra, my apologies for being obsolete and uninformed, I learned math & phsx in the very early 40s (19- that is) and did not need to refresh in my 1/2 c. of a successful R&D activity in specialty polymers. Since then (1987), however, I became an agnostic. What reverberates now is that Everett called MWI a bunch of IDENTICAL universes. In my agnostic view "MY" MWI consists of possibly no two identical universes, ours being one pretty simpleminded system - we know it only from the inside. We have no access to the others. I actually believe that the MWI is only an effective theory, an approximation to a multiverse of algorithms.It could be Bruno's theory or something else. Saibal -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI (literature)
On 12-05-2016 08:14, Bruce Kellett wrote: The proof of non-locality, even in a many worlds model, is immediate. Since the sequence under consideration comes from a series of quantum events it must violate the Bell inequalities. And Bell has shown that these inequalities must hold for any local theory. Hence quantum mechanics, even in the many worlds interpretation, is non-local. Bell showed that any local hidden variable explanation that would do away with the randomness in quantum mechanics is ruled out. This has no bearing on the MWI, or just plain QM, as the randomness remains. In the MWI the branches that effectively appear due to decoherence do not contain well defined hidden variables. Suppose e.g. that I measure the z-component if a spin that was initially polarized in the y-direction. The two branches where I find the two different outcomes can be evolved back in time, so you can write some state before I did the measurement as a superposition of these two states. But these states are not effective branches where I would get localized in before the measurement. So, Bells's theorem rules out that you can use inverse time evolution, and project out the definite future outcomes and construct a local hidden variable theory this way. Saibal -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI
On 10 May 2016 at 02:50, Brent Meeker wrote: > > > On 5/9/2016 12:52 AM, 'scerir' via Everything List wrote: > > Saibal Mitra: > > > And this is the core of the disagreement, you say that the results are > already there, but in the MWI this is false. In the MWI the cat is not > either dead or alive before you open the box, the superposition has > become entangled with the environment, but both branches are relevant > until you get to know the result. > > It seems (to me) interesting this quote from Nicolas Gisin "Against Many- > Worlds", > ch. 4 of the paper ' Are There Quantum Effects Coming from Outside Space-time? > Nonlocality, free will and "no many-worlds" ' > http://arxiv.org/pdf/1011.3440.pdf > > "On the contrary, I do not see any explanatory power in the many worlds: it > seems > to be made just to prevent one from asking (possibly provocative) questions. > Moreover, it has built in it the impossibility of any test: all its > predictions are identical > to those of quantum theory. For me, it looks like "cushion for laziness" > (un coussin de paresse in French). > > > It avoids the otherwise puzzling question of, "When does the wave function > collapse? Why is a measurement different from other physical > interactions?" QBism provides one answer, but at the cost of losing a kind > of absolute objectivity. Other solutions, like Bohm and GRW, postulate > truly different physics that produce collapse. > > And there is a second, decisive, reason to > reject > the many-worlds view: it leaves no space for free will." > > > That's a silly reason. Daniel Dennett, in his book *Elbow Room*, > explains that even Laplacian determinism leaves us all the free will worth > having. > Moreover, even if MWI did somehow destroy free will, causing some people consternation as a result, that would have no bearing on its truth. -- Stathis Papaioannou -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: Non-locality and MWI
BruceK and Smitra,my apologies for being obsolete and uninformed, I learned math & phsx in the very early 40s (19- that is) and did not need to refresh in my 1/2 c. of a successful R&D activity in specialty polymers. Since then (1987), however, I became an agnostic. What reverberates now is that Everett called MWI a bunch of IDENTICAL universes. In my agnostic view "MY" MWI consists of possibly no two identical universes, ours being one pretty simpleminded system - we know it only from the inside. We have no access to the others. John Mikes Ph.D. (chem-phys-math 1948) - 'The ‘many world interpretation seems to me an extravagant, andabove all an extravagantly vague, hypothesis. I could almostdismiss it as silly. And yet... It may have something distinctiveto say in connection to ‘Einstein Podolsky Rosen puzzle’, and itwould be worthwhile, I think, to formulate some precise versionof it to see if it really so. And the existence of all possibleworlds may make us more comfortable about existence of ourown world... which seems to be in some ways a highly improbableone." (John Bell, 1986) -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI (literature)
On 11/05/2016 11:37 pm, Bruno Marchal wrote: On 10 May 2016, at 02:10, Bruce Kellett wrote: Bell's original argument didn't mention collapse, and the argument that his theorem fails because he assumed definite outcomes from measurements is actually without substance: no such assumption is required by Bell. Bell does not mention collapse, nor EPR, because it is the assumption by default. Bell didn't mention collapse because his argument is valid whether or not you make this assumption (or the equivalent assumption of countertfactual determinism). Let me try and explain it in a different way. We have Alice with her measurement apparatus where she can make a measurement x, say, and get result a. Similarly Bob can make a measurement y and get result b. The Bell of CHSH inequalities apply to the outcomes of experiments, so we calculate probabilities (expectation values) for a sequence of joint outcomes for Alice and Bob. Since we are dealing with correlations between outcomes, the data we are working with come only after Alice and Bob have met and exchanged information. Let us call the joint result of such a meeting in one world as (ab|xy) for results a and b given settings x and y, respectively. If there are two possible outcomes for a and b, there are four such combinations in the superposition representing any run of the experiment. If, in order to estimate correlations, we do N runs of the experiment, there will be 4^N possible sequences of results for Alice and Bob, represented by: (ab|xy)_1, (ab|xy)_2, (ab|xy)_3,(ab|xy)_N, where the subscripts indicating run number actually apply to all of a,b,x, and y; and a,b can each be + or -, giving the 4^N distinct sequences. In the many worlds approach, all such sequences are realized in one world or another. All we have to do now is choose a typical world, any world, and look at that particular sequence. The sequence consists of actual measurement results, pointer setting, or whatever. And they occur after Alice and Bob have met after each trial. So this is now just a sequence of results that could have been obtained in a run of N trials in the collapse model. There is absolutely no difference in the data sequences obtained from either model. The Bell inequalities are obtained by calculating the expectation values for just such sequences: where the sequence came from -- a collapse model or selection of one world from the universal wave function -- is irrelevant for Bell's calculation. So Bell did not make explicit an collapse assumption because no such assumption is needed for his derivation. The proof of non-locality, even in a many worlds model, is immediate. Since the sequence under consideration comes from a series of quantum events it must violate the Bell inequalities. And Bell has shown that these inequalities must hold for any local theory. Hence quantum mechanics, even in the many worlds interpretation, is non-local. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
BruceK and Smitra, my apologies for being obsolete and uninformed, I learned math & phsx in the very early 40s (19- that is) and did not need to refresh in my 1/2 c. of a successful R&D activity in specialty polymers. Since then (1987), however, I became an agnostic. What reverberates now is that Everett called MWI a bunch of IDENTICAL universes. In my agnostic view "MY" MWI consists of possibly no two identical universes, ours being one pretty simpleminded system - we know it only from the inside. We have no access to the others. John Mikes Ph.D. (chem-phys-math 1948) On Tue, May 10, 2016 at 6:39 PM, Bruce Kellett wrote: > On 11/05/2016 1:54 am, smitra wrote: > >> On 10-05-2016 06:04, Bruce Kellett wrote: >> >> Non-locality was not the issue with this example of the cat in the >>> box. All I was seeking to establish was that the observer maybe on >>> definite branches of the wave function (i.e., have been "split") >>> without knowing about it. The wave function here is taken to be an >>> objective description of the system, and the observer is part of the >>> wave function. So the observer might well be on both the cat-dead and >>> cat-alive branches, but be unaware of which. The cat is definitely >>> dead on the cat-dead branch and alive on the cat-alive branch. So this >>> is an objective fact of the evolved wave function, even thought the >>> observer has no yet self-located. Opening the box then conveys >>> information to the observer, but does not kill the cat, or cause the >>> split in the wave function, or the observer. The duplicated persons >>> may objectively be, one in Washington and one in Moscow, without being >>> aware of which city (branch of the wave function) they are in. Opening >>> the door and finding out conveys information, but does not transport >>> the person to that city. >>> >> >> Yes, but even in the case of the observer getting localized without he or >> she consciously being aware of that, this localization effect will still be >> due to local interaction with the branches in the region he/she is in. So >> whether or not localization in a branch requires conscious awareness of the >> differences between the two branches isn't relevant. >> >> This means that when Alice is on her way to meet with Bob, she won't be >> localized inside Bob's branches corresponding to Bob having obtained >> definite results with definite polarizer settings, at least until that time >> she gets located inside the light cone emanating from the points at Bob's >> location at the times when the relevant information about these facts were >> created. >> > > So what? The information is already present in the wave function-- nothing > new is created when the light cones overlap. > > Bruce > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to everything-list+unsubscr...@googlegroups.com. > To post to this group, send email to everything-list@googlegroups.com. > Visit this group at https://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: R: Re: R: Re: Non-locality and MWI (literature)
Following the above reasoning MWI (if it is a truly deterministic theory) should violate the locality condition. I doubt this, but if you find a proof, in the literature (or not), I am interested. As I explained, and also give references, it seems to me that the MWI restores both 3p determinacy and 3p locality, making both the indeterminacy and non-locality only first person plural phenomenological happening. That is also Everett's position, and I would say the position of most Everettian (I still don't find any Everettian claiming that the MWI remains non-local, except the beginners who often think at first that the entire universe split instantaneously, but this does not deserve to be commented as nobody believes in this anymore). Bruno Jarrett, but also Shimony, and also Ghirardi, gave the proof that a *deterministic* QM (I should say a *deterministic and single-valued* QM) must violate the Locality Condition. I do not have references at hand, right now. I'll write down something as soon as possible. I did not re-read it, but a paper (about differences between non-separability, non-locality, determinism, etc.) could be this one http://dropcanvas.com/#n9m72p90WEc54O (I hope the link works) -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: R: Re: R: Re: Non-locality and MWI (literature)
Bruce: I came across the following brief statement by Goldstein et al: Many-worlds and relational interpretations of quantum theory [etc.] # Adrian Kent writes: "Making scientific sense of Everett’s idea is difficult, as evidenced by the many and generally incompatible attempts to show how unitary quantum theory explains the appearance of a quasiclassical world and the apparent validity of the Born rule and Copenhagen quantum theory, and evidenced also by the problems with all of these attempts. There is still nothing close to a consensus on the most promising way forward, even among many-worlds enthusiasts. This adds motivation for developing alternative ways of formulating quantum theory that have the purported advantages of many-worlds ideas — realism, and Lorentz invariance — but describe a single real world, so avoiding both the conceptual problems and the fantastic nature of many-worlds ideas. Still, for many, the appeal of many-worlds ideas evidently persists." in http://arxiv.org/abs/1408.1944 "Does it Make Sense to Speak of Self-Locating Uncertainty in the Universal Wave Function?" see also http://arxiv.org/abs/0905.0624 and http://arxiv.org/abs/gr-qc/9703089 -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI (literature)
On 10 May 2016, at 02:10, Bruce Kellett wrote: On 10/05/2016 2:22 am, Bruno Marchal wrote: On 09 May 2016, at 15:46, Bruce Kellett wrote: On 9/05/2016 10:45 pm, Bruno Marchal wrote: On 09 May 2016, at 04:12, Bruce Kellett wrote: This is the case for the discussion in section 9.1.2 of the paper by Brown and Timpson. Their equation (9) contains all the relevant results that set the universal wave function -- the additional third measurement (or measurement-like interaction) leading to equation (10) is, therefore, irrelevant. All that happens in eq. (10) is an exchange of information -- but it is an exchange of information that is already present in the universal wave function, no new information is created at this point. Just like opening the box on Schrödinger's cat, which is either alive or dead long before, looking changes nothing. Eq. (10) is, similarly, just an interpretive gloss of no fundamental significance. The important point here is that everything is set in the universal wave function before Alice and Bob meet. The relative angle of the respective polarizers is set in the wave function long before the light cones of Alice and Bob overlap, so that relative angle is determined non-locally. The universal wave function is not a local object -- I am not sure what does this mean. The SWE is linear which is a case of extreme locality I would say. Linearity does not entail locality. Where did you get that notion from? If you can show me a linear transformation which emulates something non local (and not just phenomenological), I would be interested. To have the non-locality from Bell, what we are arguing is that you need the collapse, which is not linear. No, you don't need collapse, that is the whole thrust of my argument. I have demonstrated non-locality within the Everettian approach without collapse. It seems to me that you have shown non-separability (that some call non-locality). You have no shown that in any branches where the couple Alice and Bob can talk to each other some genuine physical influence at a distance has existed. Bell's original argument didn't mention collapse, and the argument that his theorem fails because he assumed definite outcomes from measurements is actually without substance: no such assumption is required by Bell. ? Bell does not mention collapse, nor EPR, because it is the assumption by default. All you have to do to convince yourself of this is to think of my illustration of working in momentum space in order to deal with the superpositions involved in the description of a particle by a wave packet. If there are superpositions involved in the outcome of experiments, it is sufficient for calculational purposes to consider just one typical member of the superposition. The superposition can be recovered later by a convolution integral over the initial distribution. It is convenient FAPP, OK. But only when a physical collapse is supposed to be done, can we say that the inseparability entails action- at-a-distance. Without collapse, I see only contagion of superpositions propagating at sub-light speed. You can study the book by Pour-El, which contributed to my idea that linear transformation preserve local influence. My intution stem from the fact that "linear" is simpler than computable". Of course we use real numbers, and so "computable" itself does not admit standard definition on which everyone agree, so I will not insist on this. the unitary evolution does not have any implicit notion of locality. ? Locality is a human convention, and the universal wave function is under no compulsion to take any notice of human conventions or preferences. The question is only: does Alice's measurement change something instantaneously and physically at a distance? Obviously, this is not a question of convention. No, it is not a convention, and the violation of Bell and similar inequalities shows that such non-local action is present That is what you are asked to justify. And I have done so. -- the measurement at particle 2 is not independent of what happened to particle 1. There is a recent review of Bell non-locality by Brunner et al. (RMP 86 (2014) pp. 419-478) which takes non-locality as an established physical result. This would be the position of most working physicists. Because most working physicist believe there is a unique single physical reality. Argument of majority are not argument at all, also. I see clearly that such action at a distance has to occur in all QM with a physical collapse assumption, as Einstein saw already in 1927 at the Solvay Congress, and EPR-BELL-Bohm made testable. But if the collapse is a first person view entangled with the particle in the singlet state, I don't see any action at a distance occurring, even if it looks like that for the person involved. I don't
Re: R: Re: R: Re: Non-locality and MWI (literature)
On 11/05/2016 2:31 am, Bruno Marchal wrote: On 10 May 2016, at 15:37, 'scerir' via Everything List wrote: Following the above reasoning MWI (if it is a truly deterministic theory) should violate the locality condition. I doubt this, but if you find a proof, in the literature (or not), I am interested. As I explained, and also give references, it seems to me that the MWI restores both 3p determinacy and 3p locality, making both the indeterminacy and non-locality only first person plural phenomenological happening. That is also Everett's position, and I would say the position of most Everettian (I still don't find any Everettian claiming that the MWI remains non-local, except the beginners who often think at first that the entire universe split instantaneously, but this does not deserve to be commented as nobody believes in this anymore). I came across the following brief statement by Goldstein et al: *Many-worlds and relational interpretations of quantum theory** * Strictly speaking, there is yet another assumption, besides locality and the "no conspiracy" condition that is necessary for the proof of Bell's theorem: one has to assume that, after the experiment on one given side is performed, its ±1-valued outcome is a well-defined element of physical reality. (Recall that in Section 6, in order to apply Bell's definition of locality to the type of experiment considered in Section 5, we assumed that the outcomes A1 and A2 were functions of the local beables in regions 1 and 2, respectively.) Now one might wonder how anyone could deny that assumption. After all, the outcome of the experiment is recorded by the configuration of a macroscopic object (say, a pointer position, ink on a piece of paper, etc.) that can be directly inspected by a human experimenter. However, there exists one fairly popular interpretation of quantum theory that does deny that one has (after the experiments are concluded) a well-defined physically real ±1-valued outcome on each side: the many-worlds interpretation90. More precisely, according to the many-worlds interpretation, both outcomes are equally real on each side, so that it doesn't make sense to talk about "the one ±1-valued outcome that actually occurs". Certain "relational" interpretations of quantum theory91 also deny that a completed experiment has a well-defined physically real outcome. It is possible that this type of strategy could succeed in evading the consequences of Bell's theorem, allowing for the possibility of a universe governed by a local theory such that conscious observers living in that universe attest to the validity of the quantum predictions. However, it is not clear how to actually do the trick. There are many difficulties and the subject is rather subtle. To begin with, there are controversies around the problem of finding an appropriate formulation of a many-worlds (or relational) interpretation. Moreover, it is not clear whether such an appropriate formulation can be made local, given that the wave function — which seems to be all there is in standard formulations of many-worlds theories — is not a localized object; in the terminology of Bell, it is not a local beable. (Indeed, if a theory has no local beables, it is certainly not meaningful to ask whether it is local or not in the relevant sense.) A formulation of a version of the many-worlds interpretation which includes, in addition to the wave function, some local beables, was presented in a recent paper92, but it was found by the authors to be non-local. The question of whether a many-worlds (or relational) approach can be taken advantage of to create a local (and empirically viable) theory thus remains open — as does the question of how seriously one should take a theory of this type, should it be successfully constructed. http://www.scholarpedia.org/article/Bell%27s_theorem#Manyworlds_and_relational_interpretations_of_quantum_theory This Scholarpedia article (*6*, 8378) is available on-line and has many additional references. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: R: Re: Non-locality and MWI (literature)
On 11/05/2016 2:31 am, Bruno Marchal wrote: The question is: are the probabilities, or the indeterminacies, and the non locality, phenomenological (1p) or factual (ontological, real, 3p)? QM+collapse admit factual indeterminacies (God plays dice, and there are action at a distance, even if they cannot be used to transmit signal quicker than light). QM-without-collapse is purely deterministic at the 3p level, and admits indeterminacies at the phenomenological level. I think everyone agree on this. I think that your confidence here is a bit premature. The Schrödinger equation was devised for the quantum behaviour of a single non-relativistic particle. It is local and deterministic in the many worlds interpretation for that case. However, the Schrödinger equation does not relate easily to relativity or spin degrees of freedom (spin is an intrinsically relativistic notion). These can be tacked on, but not always with great felicity. The main problem, however, is that once you move beyond a single particle system, you have to move from physical space into configuration space, where there are three independent 'spatial' coordinates for each particle. This caused consternation for the early practitioners of QM, and still causes problems today for the overly naïve. So while the Schrödinger equation for a multi-particle system might be local and deterministic in configuration space, there is no guarantee that this will remain true when one moves back into physical space to confront experiment. This is precisely the problem that one encounters with the current example of entangled pairs of spinning particles. Single particle non-relativistic intuitions can mislead, and do so here. Your confidence in determinism and locality for this system is seriously misplaced. The debate is on the following question: does QM-without-collapse admit factual non-locality (real physical action at a distance, like QM-with-collapse), or do the non-locality becomes, like the indeterminacy, phenomenological? (I think yes, as Jesse, Saibal and others, but it seems Bruce and John C. differ on this). Given that one cannot simply assume locality or determinism for the multi-particle system, one is led back to the Bell and CHSH inequalities. These apply to the two particle case, and the experimental confirmation of the violation of these inequalities for entangled particles leads to the conclusion that quantum mechanics is intrinsically non-local. Since Everettian QM is claimed to reproduce all the standard quantum results, it must also violate these inequalities. So either Everettian QM is as non-local as standard QM, or the Bell and CHSH theorems do not apply to the no-collapse theory. This latter has been claimed, and people have sought for assumptions that these theorems make that are not true in MWI. For example, Price claims: "Bell and Eberhard had implicity assumed that every possible measurement - even if not performed - would have yielded a /single/ definite result. This assumption is called contra-factual definiteness or CFD [S]. What Bell and Eberhard really proved was that every quantum theory must either violate locality /or/ CFD." The trouble here is that CFD is either trivially violated in ordinary quantum mechanics, or it is without content. CFD, if it is to mean anything at all, would be the claim that an unperformed experiment would produce a definite result *that could be predicted in advance*. That is, of course false in any version of quantum mechanics. An unperformed experiment would necessarily produce a result, not necessarily predictable, in a collapse model; and all possible results in a many worlds model. But in neither case is there any lack of a result. So the notion of CFD remains murky, and its relevance to the Bell and CHSH derivations is even less clear -- in exactly which line of the proofs is that assumption made? and what happens if that assumption is not made? I think the claim of counterfactual indefiniteness, if it means anything, reduces to the claim that Bell assumes a collapse model. This is the other argument that is raised against the Bell and CHSH proofs -- they assume that experiments have single outcomes. In other words, they assume a collapse model. But this is not true either, or, if it is true, it is not fatal to the applicability of these theorems to MWI. I will post a full derivation of the CHSH inequality shortly, and I claim that this does not make any assumption about single results. In fact, the whole proof is cast in terms of expectation values over results, so this works for both single and multiple outcomes for any particular experiment. The proof is not invalidated by moving to a many worlds scenario because, for any particular set of outcomes from the measurements on each of the entangled particles, there is only a finite number of possible joint worlds that can be produced. Each of these is
Re: Non-locality and MWI
On 11-05-2016 00:39, Bruce Kellett wrote: On 11/05/2016 1:54 am, smitra wrote: On 10-05-2016 06:04, Bruce Kellett wrote: Non-locality was not the issue with this example of the cat in the box. All I was seeking to establish was that the observer maybe on definite branches of the wave function (i.e., have been "split") without knowing about it. The wave function here is taken to be an objective description of the system, and the observer is part of the wave function. So the observer might well be on both the cat-dead and cat-alive branches, but be unaware of which. The cat is definitely dead on the cat-dead branch and alive on the cat-alive branch. So this is an objective fact of the evolved wave function, even thought the observer has no yet self-located. Opening the box then conveys information to the observer, but does not kill the cat, or cause the split in the wave function, or the observer. The duplicated persons may objectively be, one in Washington and one in Moscow, without being aware of which city (branch of the wave function) they are in. Opening the door and finding out conveys information, but does not transport the person to that city. Yes, but even in the case of the observer getting localized without he or she consciously being aware of that, this localization effect will still be due to local interaction with the branches in the region he/she is in. So whether or not localization in a branch requires conscious awareness of the differences between the two branches isn't relevant. This means that when Alice is on her way to meet with Bob, she won't be localized inside Bob's branches corresponding to Bob having obtained definite results with definite polarizer settings, at least until that time she gets located inside the light cone emanating from the points at Bob's location at the times when the relevant information about these facts were created. So what? The information is already present in the wave function-- nothing new is created when the light cones overlap. The localization of Alice inside Bob's branches and vice versa can only start at that point. Decoherence happens fast but this entanglement involving more and more of he environmental degrees of freedom can only spread at the speed of light. This means that the MWI does not have the same issue w.r.t. non-locality as collapse interpretations have where only one branch is real. Saibal -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 11/05/2016 1:54 am, smitra wrote: On 10-05-2016 06:04, Bruce Kellett wrote: Non-locality was not the issue with this example of the cat in the box. All I was seeking to establish was that the observer maybe on definite branches of the wave function (i.e., have been "split") without knowing about it. The wave function here is taken to be an objective description of the system, and the observer is part of the wave function. So the observer might well be on both the cat-dead and cat-alive branches, but be unaware of which. The cat is definitely dead on the cat-dead branch and alive on the cat-alive branch. So this is an objective fact of the evolved wave function, even thought the observer has no yet self-located. Opening the box then conveys information to the observer, but does not kill the cat, or cause the split in the wave function, or the observer. The duplicated persons may objectively be, one in Washington and one in Moscow, without being aware of which city (branch of the wave function) they are in. Opening the door and finding out conveys information, but does not transport the person to that city. Yes, but even in the case of the observer getting localized without he or she consciously being aware of that, this localization effect will still be due to local interaction with the branches in the region he/she is in. So whether or not localization in a branch requires conscious awareness of the differences between the two branches isn't relevant. This means that when Alice is on her way to meet with Bob, she won't be localized inside Bob's branches corresponding to Bob having obtained definite results with definite polarizer settings, at least until that time she gets located inside the light cone emanating from the points at Bob's location at the times when the relevant information about these facts were created. So what? The information is already present in the wave function-- nothing new is created when the light cones overlap. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: R: Re: R: Re: R: Re: Non-locality and MWI (literature)
. I think we all agree that QM-with-collapse entails a violation of Locality. The debate was for the case of the non-single value QM, that is QM-without-collapse, where all branches of the wave are kept "alive". Bruno As somebody wrote "Algebraic nonseparability entails geometric nonlocality; emphasis on its time aspect can be worded atemporality." (Olivier Costa de Beauregard). And yes, in QM without collapse (without reduction of probability packet), all branches are kept alive (with some probability or weight attached to each world; with a conservation of energy not well defined in each world or, better, during each split; and with a strange concept of locality - because there are "many" decohering "worlds"). s. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: R: Re: R: Re: Non-locality and MWI (literature)
On 10 May 2016, at 19:06, 'scerir' via Everything List wrote: Messaggio originale Da: Bruno Marchal Data: 10/05/2016 18.31 A: Ogg: Re: R: Re: R: Re: Non-locality and MWI (literature) On 10 May 2016, at 15:37, 'scerir' via Everything List wrote: Thanks Scerir, but yet again, this paper get the same conclusion as mine (and most people here). With the MWI, non-locality does not imply action-at-a distance. (d'Espagnat would call it non- separability). What I look for would be a paper which would show that in the MWI there are action-at-a-distance, like Bruce and John C claim. I might comment later, as I am late in my scheduling, but will just notice that Gisin's paper (mentionned by Brent) use the non- compatibilist theory of free-will, which makes no-sense to a mechanist. I think Brent concluded similarly. Bruno If A and B are two wings of a typical Bell apparatus, i the observable to be measured in A and x its possible value, j is the observable to be measured in B and y its possible value, and if Lambda are hidden variables, we could write Locality Condition p_A,Lambda (x|i,j) = p_A,Lambda (x|i) p_B,Lambda (y|i,j) = p_B,Lambda (y|j) Separability Condition p_A,Lambda (x|i,j,y) = p_A,Lambda (x|i,j) p_B,Lambda (y|i,j,x) = P_B,Lambda (y|i,j) There is (was) some agreement that a (phantomatic) deterministic theory (i.e. one in which the range of any probability distribution of outcomes is the set: 0 or 1) ? The question is: are the probabilities, or the indeterminacies, and the non locality, phenomenological (1p) or factual (ontological, real, 3p)? QM+collapse admit factual indeterminacies (God plays dice, and there are action at a distance, even if they cannot be used to transmit signal quicker than light). QM-without-collapse is purely deterministic at the 3p level, and admits indeterminacies at the phenomenological level. I think everyone agree on this. The debate is on the following question: does QM-without-collapse admit factual non-locality (real physical action at a distance, like QM-with-collapse), or do the non-locality becomes, like the indeterminacy, phenomenological? (I think yes, as Jesse, Saibal and others, but it seems Bruce and John C. differ on this). Frankly it is not easy for me to say anything about that, at least something consistent. Mainly because "Many-worlds with its multiplicity of results in different worlds violates CFD, of course, and thus can be local. Thus many-worlds is the only local quantum theory in accord with the standard predictions of QM and, so far, with experiment.". reproducing all the predictions of QM, can not violate the Separability Condition, (the specification of Lambda, i, j, in principle determines completely the outcomes x, y, then any additional conditioning on x or y is superfluous, having x and y just one value allowed, so they cannot affect the probability, which - in a deterministic theory - can just take the values 0 or 1) and must violate the Locality Condition. Following the above reasoning MWI (if it is a truly deterministic theory) should violate the locality condition. I doubt this, but if you find a proof, in the literature (or not), I am interested. As I explained, and also give references, it seems to me that the MWI restores both 3p determinacy and 3p locality, making both the indeterminacy and non-locality only first person plural phenomenological happening. That is also Everett's position, and I would say the position of most Everettian (I still don't find any Everettian claiming that the MWI remains non-local, except the beginners who often think at first that the entire universe split instantaneously, but this does not deserve to be commented as nobody believes in this anymore). Bruno Jarrett, but also Shimony, and also Ghirardi, gave the proof that a *deterministic* QM (I should say a *deterministic and single- valued* QM) Yes, that is important to add. It was notoriously implicit in EPR and Bell 1964, even after. must violate the Locality Condition. EPR and Bell shows this, and the usual papers (Clauser and Horne, Clauser Horne Shimony, Holt, Aspect, ...). I do not have references at hand, right now. I'll write down something as soon as possible. I think we all agree that QM-with-collapse entails a violation of Locality. The debate was for the case of the non-single value QM, that is QM-without-collapse, where all branches of the wave are kept "alive". Bruno -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything- l...@googlegroups.com. Visit this group
Re: R: Re: R: Re: Non-locality and MWI (literature)
On 10 May 2016, at 18:36, 'scerir' via Everything List wrote: scerir wrote: If A and B are two wings of a typical Bell apparatus, i the observable to be measured in A and x its possible value, j is the observable to be measured in B and y its possible value, and if Lambda are hidden variables, we could write Locality Condition p_A,Lambda (x|i,j) = p_A,Lambda (x|i) p_B,Lambda (y|i,j) = p_B,Lambda (y|j) Separability Condition p_A,Lambda (x|i,j,y) = p_A,Lambda (x|i,j) p_B,Lambda (y|i,j,x) = p_B,Lambda (y|i,j) There is (or was) some agreement that a (phantomatic) deterministic theory (i.e. one in which the range of any probability distribution of outcomes is the set: 0 or 1) reproducing all the predictions of QM, can not violate the Separability Condition, (the specification of Lambda, i, j, in principle determines completely the outcomes x, y, then any additional conditioning on x or y is superfluous, having x and y just one value allowed, so they cannot affect the probability, which - in a deterministic theory - can just take the values 0 or 1) and must violate the Locality Condition. Following the above reasoning, MWI (if it is a truly deterministic theory) should violate the Locality Condition. --- ### Since the Everett faq gives the following . "To recap. Many-worlds is local and deterministic. Local measurements split local systems (including observers) in a subjectively random fashion; distant systems are only split when the causally transmitted effects of the local interactions reach them. We have not assumed any non-local FTL effects, yet we have reproduced the standard predictions of QM. So where did Bell and Eberhard go wrong? They thought that all theories that reproduced the standard predictions must be non-local. It has been pointed out by both Albert [A] and Cramer [C] (who both support different interpretations of QM) that Bell and Eberhard had implicity assumed that every possible measurement - even if not performed - would have yielded a single definite result. This assumption is called contra- factual definiteness or CFD [S]. What Bell and Eberhard really proved was that every quantum theory must either violate locality or CFD. Many-worlds with its multiplicity of results in different worlds violates CFD, of course, and thus can be local." So, I should say that . MWI (if it is a truly deterministic theory, reproducing all the predictions of QM) should violate the Locality Condition but, in fact, it violates CFD only :-). Exactly. I think we are on the same length wave (as we say in french for assessment). And that is why QM-without collapse needs only the computationalist First Person Indeterminacy (FPI), making QM facts confirming mechanism instead of threatening it (which is what would happen if we allow collapse, or worst, direct action of consciousness on the physical). Like with Gödels theorem, QM seems to threat mechanism, but eventually appears to be an ally, and perhaps a confirmation, (which of course is not a proof, but we can't prove anything on reality, nor even that it exists. We can only bet on it.). Bruno -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: R: Re: R: Re: Non-locality and MWI (literature)
Messaggio originale Da: Bruno Marchal Data: 10/05/2016 18.31 A: Ogg: Re: R: Re: R: Re: Non-locality and MWI (literature) On 10 May 2016, at 15:37, 'scerir' via Everything List wrote: Thanks Scerir, but yet again, this paper get the same conclusion as mine (and most people here). With the MWI, non-locality does not imply action-at-a distance. (d'Espagnat would call it non-separability). What I look for would be a paper which would show that in the MWI there are action-at-a-distance, like Bruce and John C claim. I might comment later, as I am late in my scheduling, but will just notice that Gisin's paper (mentionned by Brent) use the non-compatibilist theory of free-will, which makes no-sense to a mechanist. I think Brent concluded similarly. Bruno If A and B are two wings of a typical Bell apparatus, i the observable to be measured in A and x its possible value, j is the observable to be measured in B and y its possible value, and if Lambda are hidden variables, we could write Locality Condition p_A,Lambda (x|i,j) = p_A,Lambda (x|i) p_B,Lambda (y|i,j) = p_B,Lambda (y|j) Separability Condition p_A,Lambda (x|i,j,y) = p_A,Lambda (x|i,j) p_B,Lambda (y|i,j,x) = P_B,Lambda (y|i,j) There is (was) some agreement that a (phantomatic) deterministic theory (i.e. one in which the range of any probability distribution of outcomes is the set: 0 or 1) ? The question is: are the probabilities, or the indeterminacies, and the non locality, phenomenological (1p) or factual (ontological, real, 3p)? QM+collapse admit factual indeterminacies (God plays dice, and there are action at a distance, even if they cannot be used to transmit signal quicker than light). QM-without-collapse is purely deterministic at the 3p level, and admits indeterminacies at the phenomenological level. I think everyone agree on this. The debate is on the following question: does QM-without-collapse admit factual non-locality (real physical action at a distance, like QM-with-collapse), or do the non-locality becomes, like the indeterminacy, phenomenological? (I think yes, as Jesse, Saibal and others, but it seems Bruce and John C. differ on this). Frankly it is not easy for me to say anything about that, at least something consistent. Mainly because "Many-worlds with its multiplicity of results in different worlds violates CFD, of course, and thus can be local. Thus many-worlds is the only local quantum theory in accord with the standard predictions of QM and, so far, with experiment.". reproducing all the predictions of QM, can not violate the Separability Condition, (the specification of Lambda, i, j, in principle determines completely the outcomes x, y, then any additional conditioning on x or y is superfluous, having x and y just one value allowed, so they cannot affect the probability, which - in a deterministic theory - can just take the values 0 or 1) and must violate the Locality Condition. Following the above reasoning MWI (if it is a truly deterministic theory) should violate the locality condition. I doubt this, but if you find a proof, in the literature (or not), I am interested. As I explained, and also give references, it seems to me that the MWI restores both 3p determinacy and 3p locality, making both the indeterminacy and non-locality only first person plural phenomenological happening. That is also Everett's position, and I would say the position of most Everettian (I still don't find any Everettian claiming that the MWI remains non-local, except the beginners who often think at first that the entire universe split instantaneously, but this does not deserve to be commented as nobody believes in this anymore). Bruno Jarrett, but also Shimony, and also Ghirardi, gave the proof that a *deterministic* QM (I should say a *deterministic and single-valued* QM) must violate the Locality Condition. I do not have references at hand, right now. I'll write down something as soon as possible. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: R: Re: Non-locality and MWI (literature)
scerir wrote: If A and B are two wings of a typical Bell apparatus, i the observable to be measured in A and x its possible value, j is the observable to be measured in B and y its possible value, and if Lambda are hidden variables, we could write Locality Condition p_A,Lambda (x|i,j) = p_A,Lambda (x|i) p_B,Lambda (y|i,j) = p_B,Lambda (y|j) Separability Condition p_A,Lambda (x|i,j,y) = p_A,Lambda (x|i,j) p_B,Lambda (y|i,j,x) = p_B,Lambda (y|i,j) There is (or was) some agreement that a (phantomatic) deterministic theory (i.e. one in which the range of any probability distribution of outcomes is the set: 0 or 1) reproducing all the predictions of QM, can not violate the Separability Condition, (the specification of Lambda, i, j, in principle determines completely the outcomes x, y, then any additional conditioning on x or y is superfluous, having x and y just one value allowed, so they cannot affect the probability, which - in a deterministic theory - can just take the values 0 or 1) and must violate the Locality Condition. Following the above reasoning, MWI (if it is a truly deterministic theory) should violate the Locality Condition. --- ### Since the Everett faq gives the following . "To recap. Many-worlds is local and deterministic. Local measurements split local systems (including observers) in a subjectively random fashion; distant systems are only split when the causally transmitted effects of the local interactions reach them. We have not assumed any non-local FTL effects, yet we have reproduced the standard predictions of QM. So where did Bell and Eberhard go wrong? They thought that all theories that reproduced the standard predictions must be non-local. It has been pointed out by both Albert [A] and Cramer [C] (who both support different interpretations of QM) that Bell and Eberhard had implicity assumed that every possible measurement - even if not performed - would have yielded a single definite result. This assumption is called contra-factual definiteness or CFD [S]. What Bell and Eberhard really proved was that every quantum theory must either violate locality or CFD. Many-worlds with its multiplicity of results in different worlds violates CFD, of course, and thus can be local." So, I should say that . MWI (if it is a truly deterministic theory, reproducing all thepredictions of QM) should violate the Locality Condition but, in fact, it violates CFD only :-). -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: R: Re: Non-locality and MWI (literature)
On 10 May 2016, at 15:37, 'scerir' via Everything List wrote: Thanks Scerir, but yet again, this paper get the same conclusion as mine (and most people here). With the MWI, non-locality does not imply action-at-a distance. (d'Espagnat would call it non- separability). What I look for would be a paper which would show that in the MWI there are action-at-a-distance, like Bruce and John C claim. I might comment later, as I am late in my scheduling, but will just notice that Gisin's paper (mentionned by Brent) use the non- compatibilist theory of free-will, which makes no-sense to a mechanist. I think Brent concluded similarly. Bruno If A and B are two wings of a typical Bell apparatus, i the observable to be measured in A and x its possible value, j is the observable to be measured in B and y its possible value, and if Lambda are hidden variables, we could write Locality Condition p_A,Lambda (x|i,j) = p_A,Lambda (x|i) p_B,Lambda (y|i,j) = p_B,Lambda (y|j) Separability Condition p_A,Lambda (x|i,j,y) = p_A,Lambda (x|i,j) p_B,Lambda (y|i,j,x) = P_B,Lambda (y|i,j) There is (was) some agreement that a (phantomatic) deterministic theory (i.e. one in which the range of any probability distribution of outcomes is the set: 0 or 1) ? The question is: are the probabilities, or the indeterminacies, and the non locality, phenomenological (1p) or factual (ontological, real, 3p)? QM+collapse admit factual indeterminacies (God plays dice, and there are action at a distance, even if they cannot be used to transmit signal quicker than light). QM-without-collapse is purely deterministic at the 3p level, and admits indeterminacies at the phenomenological level. I think everyone agree on this. The debate is on the following question: does QM-without-collapse admit factual non-locality (real physical action at a distance, like QM-with-collapse), or do the non-locality becomes, like the indeterminacy, phenomenological? (I think yes, as Jesse, Saibal and others, but it seems Bruce and John C. differ on this). reproducing all the predictions of QM, can not violate the Separability Condition, (the specification of Lambda, i, j, in principle determines completely the outcomes x, y, then any additional conditioning on x or y is superfluous, having x and y just one value allowed, so they cannot affect the probability, which - in a deterministic theory - can just take the values 0 or 1) and must violate the Locality Condition. Following the above reasoning MWI (if it is a truly deterministic theory) should violate the locality condition. I doubt this, but if you find a proof, in the literature (or not), I am interested. As I explained, and also give references, it seems to me that the MWI restores both 3p determinacy and 3p locality, making both the indeterminacy and non-locality only first person plural phenomenological happening. That is also Everett's position, and I would say the position of most Everettian (I still don't find any Everettian claiming that the MWI remains non-local, except the beginners who often think at first that the entire universe split instantaneously, but this does not deserve to be commented as nobody believes in this anymore). Bruno -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 10-05-2016 06:04, Bruce Kellett wrote: Non-locality was not the issue with this example of the cat in the box. All I was seeking to establish was that the observer maybe on definite branches of the wave function (i.e., have been "split") without knowing about it. The wave function here is taken to be an objective description of the system, and the observer is part of the wave function. So the observer might well be on both the cat-dead and cat-alive branches, but be unaware of which. The cat is definitely dead on the cat-dead branch and alive on the cat-alive branch. So this is an objective fact of the evolved wave function, even thought the observer has no yet self-located. Opening the box then conveys information to the observer, but does not kill the cat, or cause the split in the wave function, or the observer. The duplicated persons may objectively be, one in Washington and one in Moscow, without being aware of which city (branch of the wave function) they are in. Opening the door and finding out conveys information, but does not transport the person to that city. Yes, but even in the case of the observer getting localized without he or she consciously being aware of that, this localization effect will still be due to local interaction with the branches in the region he/she is in. So whether or not localization in a branch requires conscious awareness of the differences between the two branches isn't relevant. This means that when Alice is on her way to meet with Bob, she won't be localized inside Bob's branches corresponding to Bob having obtained definite results with definite polarizer settings, at least until that time she gets located inside the light cone emanating from the points at Bob's location at the times when the relevant information about these facts were created. Saibal -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: R: Re: Non-locality and MWI (literature)
Thanks Scerir, but yet again, this paper get the same conclusion as mine (and most people here). With the MWI, non-locality does not imply action-at-a distance. (d'Espagnat would call it non-separability). What I look for would be a paper which would show that in the MWI there are action-at-a-distance, like Bruce and John C claim. I might comment later, as I am late in my scheduling, but will just notice that Gisin's paper (mentionned by Brent) use the non-compatibilist theory of free-will, which makes no-sense to a mechanist. I think Brent concluded similarly. Bruno If A and B are two wings of a typical Bell apparatus, i the observable to be measured in A and x its possible value, j is the observable to be measured in B and y its possible value, and if Lambda are hidden variables, we could write Locality Condition p_A,Lambda (x|i,j) = p_A,Lambda (x|i) p_B,Lambda (y|i,j) = p_B,Lambda (y|j) Separability Condition p_A,Lambda (x|i,j,y) = p_A,Lambda (x|i,j) p_B,Lambda (y|i,j,x) = P_B,Lambda (y|i,j) There is (was) some agreement that a (phantomatic) deterministic theory (i.e. one in which the range of any probability distribution of outcomes is the set: 0 or 1) reproducing all the predictions of QM, can not violate the Separability Condition, (the specification of Lambda, i, j, in principle determines completely the outcomes x, y, then any additional conditioning on x or y is superfluous, having x and y just one value allowed, so they cannot affect the probability, which - in a deterministic theory - can just take the values 0 or 1) and must violate the Locality Condition. Following the above reasoning MWI (if it is a truly deterministic theory) should violate the locality condition. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI (literature)
On 10/05/2016 10:31 pm, Bruno Marchal wrote: On 10 May 2016, at 09:00, 'scerir' via Everything List wrote: Bruno (I suppose) wrote: But in the MWI, some work needs to be done (at least) to convince me. I don't even find a paper on the subject, only paper which shows that MWI is local (some more rigorous than other). Do you have a reference of a paper showing that Bell's inequality violation entails non locality in the MWI? I would like to take a look on it, if it exists. ### W. Myrvold wrote something here http://philsci-archive.pitt.edu/11654/ (see ch. 0.8) Thanks Scerir, but yet again, this paper get the same conclusion as mine (and most people here). With the MWI, non-locality does not imply action-at-a distance. (d'Espagnat would call it non-separability). There seems to be a degree of terminological confusion surrounding this topic. Non-locality, for me, means that the measurement at A influences the measurement at B. But this influence is not manipulable, so it cannot be used for signalling. In other words, quantum mechanics obeys the standard no-signalling theorems (and is thus consistent with special relativity), while being non-local in the sense that the measurements at A and B are not independent. Call this non-separability if you will -- the terminology should not make any difference, provided we are clear as to what the terms mean. Bruce What I look for would be a paper which would show that in the MWI there are action-at-a-distance, like Bruce and John C claim. I might comment later, as I am late in my scheduling, but will just notice that Gisin's paper (mentionned by Brent) use the non-compatibilist theory of free-will, which makes no-sense to a mechanist. I think Brent concluded similarly. Bruno -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI (literature)
On 10 May 2016, at 09:00, 'scerir' via Everything List wrote: Bruno (I suppose) wrote: But in the MWI, some work needs to be done (at least) to convince me. I don't even find a paper on the subject, only paper which shows that MWI is local (some more rigorous than other). Do you have a reference of a paper showing that Bell's inequality violation entails non locality in the MWI? I would like to take a look on it, if it exists. ### W. Myrvold wrote something here http://philsci-archive.pitt.edu/11654/ (see ch. 0.8) Thanks Scerir, but yet again, this paper get the same conclusion as mine (and most people here). With the MWI, non-locality does not imply action-at-a distance. (d'Espagnat would call it non-separability). What I look for would be a paper which would show that in the MWI there are action-at-a-distance, like Bruce and John C claim. I might comment later, as I am late in my scheduling, but will just notice that Gisin's paper (mentionned by Brent) use the non- compatibilist theory of free-will, which makes no-sense to a mechanist. I think Brent concluded similarly. Bruno -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: R: Re: Non-locality and MWI (literature)
### W. Myrvold wrote something here http://philsci-archive.pitt.edu/11654/ (see ch. 0.8) It seems that he is saying that 'action-at-a-distance' is something that would violate the 'no-signalling theorem' of quantum mechanics. So he sees experimental violation of the Bell inequalities as evidence for non-locality, but not necessarily evidence for action-at-a-distance in the above sense. I would agree with his conclusion that both collapse and Everettian theories are like this -- non-local, but also non-signalling at spacelike separations. Bruce ### Yes, It seems so. There is - in general - some confusion between 'nonlocality' and 'nonseparability'. Not to mention also 'action-at-a-distance' and 'locality of measurement' and "local causality" and so on. Myrvold et al. wrote something else here http://philsci-archive.pitt.edu/4222/1/everett_and_evidence_21aug08.pdf (general objections to Everettism). "Now it is precisely in cleaning up intuitive ideas for mathematics that one is likely to throw out the baby with the bathwater." J.S. Bell (quoted here https://arxiv.org/pdf/1007.3724.pdf ) -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI (literature)
On 10/05/2016 5:00 pm, 'scerir' via Everything List wrote: Bruno (I suppose) wrote: But in the MWI, some work needs to be done (at least) to convince me. I don't even find a paper on the subject, only paper which shows that MWI is local (some more rigorous than other). Do you have a reference of a paper showing that Bell's inequality violation entails non locality in the MWI? I would like to take a look on it, if it exists. ### W. Myrvold wrote something here http://philsci-archive.pitt.edu/11654/ (see ch. 0.8) It seems that he is saying that 'action-at-a-distance' is something that would violate the 'no-signalling theorem' of quantum mechanics. So he sees experimental violation of the Bell inequalities as evidence for non-locality, but not necessarily evidence for action-at-a-distance in the above sense. I would agree with his conclusion that both collapse and Everettian theories are like this -- non-local, but also non-signalling at spacelike separations. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: Non-locality and MWI (literature)
Bruno (I suppose) wrote: But in the MWI, some work needs to be done (at least) to convince me. I don't even find a paper on the subject, only paper which shows that MWI is local (some more rigorous than other). Do you have a reference of a paper showing that Bell's inequality violation entails non locality in the MWI? I would like to take a look on it, if it exists. ### W. Myrvold wrote something here http://philsci-archive.pitt.edu/11654/ (see ch. 0.8) -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 10/05/2016 1:06 pm, smitra wrote: On 10-05-2016 01:35, Bruce Kellett wrote: On 10/05/2016 2:42 am, smitra wrote: On 09-05-2016 07:43, Bruce Kellett wrote: On 9/05/2016 3:17 pm, smitra wrote: On 09-05-2016 03:40, Bruce Kellett wrote: The idea that Alice splits further into different branches according to Bob's results only after their respective light cones overlap is an interpretive gloss on the theory (which, as already pointed out, you do not apply consistently) -- it is not there in the mathematics. Alice and Bob are in the same world even at spacelike separations. This must be the case, or else my feet would be in a different world from my head at every single instant of time. So Bob and Alice separate in the same world. When they perform their measurements there is a Bob in each world created by Alice's results, and an Alice in every world created by Bob's results. The fact that neither Alice nor Bob do not know the other's result does not mean that there are no such results. Are there separate worlds in which these results are combined? It doesn't really matter, because anything that can be seen when information is exchanged is already set: the exchange of information is like opening the box -- the cat is already either alive or dead, opening the box does not change that. So Alice and Bob talking to each other does not change anything either. The results are already present in the universal wave function -- talk of splitting into worlds is irrelevant to the universal wave function and the unitary dynamics. So the fact that A does not know B's results at some time is irrelevant -- the results are already there. The question of who knows what is not a relevant question for the universal wave function. And the universal wave function takes account of the unity of the singlet state and the reality of non-local effects. And this is the core of the disagreement, you say that the results are already there, but in the MWI this is false. What? Are you claiming the the universal wave function -- which contains all possible branches corresponding to all possible outcomes -- does not contain the results? I think what you mean is that you do not know the result (which branch you are on) until you open the box. But that does not mean that you are not on one branch or the other. The death of the cat (if it be so) can be in your past light cone, so the splitting of worlds occasioned by that death has already split you. Your knowledge of this is strictly irrelevant. You can be in a particular world without being aware of it. In Bruno's famous person duplication experiments, you are in either Washington or Moscow before you are necessarily ever aware of which city it is. You make personal knowledge of outcomes far too prominent in your theory; things can actually happen without your being aware of them! While your body does split up, if you don't have the "which branch" information then you are in both branches until that time that you do have this information. Nah. That places far too much emphasis on the conscious mind -- making "what you know" the determiner of physical reality. I think Brent might refer to this as QBism (Quantum Bayesianism). A person is more than just what they happen to be thinking at the moment. If the body participates in the split, the brain also so participates. Instantaneous conscious (or computational) states are transient, and will be influenced by many external influences. Your suggestion, if taken literally, would have us fluctuating uncontrollably between one world or many. Not a good idea. I think we have to gives some significance to the objective state of the wave function. That is what is determined by unitary evolution; what we think about it is irreducibly secondary. One has to be more rigorous about including the observer here. In the MWI there is no excuse to not do this as it's a complete theory and in this discussion we're assuming that the MWI is correct, which supposedly leads to a problem with non-locality just as in collapse interpretations. So, the computational state you are in at some moment may contain noise. Even if that noise is perfectly correlated with the state of the cat, this would then mean that you end up in a branch where the fate of the cat is determined due to the addition of the noise in your brain. There is then no difference between the noiseless case as far as the necessity for a local interaction is concerned (we're replacing explicit communication of the facts with implicit information transfer via noise). If we consider ourselves as programs run by our brains and consider some well defined computational state, look at all the branches where that particular computational state is implemented, then you'll find that it's present in both situations where the information about the cat is different. Hmm. I think there may be a typo here. If the information about the cat is different, it would suggest
Re: Non-locality and MWI
On 10-05-2016 01:35, Bruce Kellett wrote: On 10/05/2016 2:42 am, smitra wrote: On 09-05-2016 07:43, Bruce Kellett wrote: On 9/05/2016 3:17 pm, smitra wrote: On 09-05-2016 03:40, Bruce Kellett wrote: The idea that Alice splits further into different branches according to Bob's results only after their respective light cones overlap is an interpretive gloss on the theory (which, as already pointed out, you do not apply consistently) -- it is not there in the mathematics. Alice and Bob are in the same world even at spacelike separations. This must be the case, or else my feet would be in a different world from my head at every single instant of time. So Bob and Alice separate in the same world. When they perform their measurements there is a Bob in each world created by Alice's results, and an Alice in every world created by Bob's results. The fact that neither Alice nor Bob do not know the other's result does not mean that there are no such results. Are there separate worlds in which these results are combined? It doesn't really matter, because anything that can be seen when information is exchanged is already set: the exchange of information is like opening the box -- the cat is already either alive or dead, opening the box does not change that. So Alice and Bob talking to each other does not change anything either. The results are already present in the universal wave function -- talk of splitting into worlds is irrelevant to the universal wave function and the unitary dynamics. So the fact that A does not know B's results at some time is irrelevant -- the results are already there. The question of who knows what is not a relevant question for the universal wave function. And the universal wave function takes account of the unity of the singlet state and the reality of non-local effects. And this is the core of the disagreement, you say that the results are already there, but in the MWI this is false. What? Are you claiming the the universal wave function -- which contains all possible branches corresponding to all possible outcomes -- does not contain the results? I think what you mean is that you do not know the result (which branch you are on) until you open the box. But that does not mean that you are not on one branch or the other. The death of the cat (if it be so) can be in your past light cone, so the splitting of worlds occasioned by that death has already split you. Your knowledge of this is strictly irrelevant. You can be in a particular world without being aware of it. In Bruno's famous person duplication experiments, you are in either Washington or Moscow before you are necessarily ever aware of which city it is. You make personal knowledge of outcomes far too prominent in your theory; things can actually happen without your being aware of them! While your body does split up, if you don't have the "which branch" information then you are in both branches until that time that you do have this information. Nah. That places far too much emphasis on the conscious mind -- making "what you know" the determiner of physical reality. I think Brent might refer to this as QBism (Quantum Bayesianism). A person is more than just what they happen to be thinking at the moment. If the body participates in the split, the brain also so participates. Instantaneous conscious (or computational) states are transient, and will be influenced by many external influences. Your suggestion, if taken literally, would have us fluctuating uncontrollably between one world or many. Not a good idea. I think we have to gives some significance to the objective state of the wave function. That is what is determined by unitary evolution; what we think about it is irreducibly secondary. One has to be more rigorous about including the observer here. In the MWI there is no excuse to not do this as it's a complete theory and in this discussion we're assuming that the MWI is correct, which supposedly leads to a problem with non-locality just as in collapse interpretations. So, the computational state you are in at some moment may contain noise. Even if that noise is perfectly correlated with the state of the cat, this would then mean that you end up in a branch where the fate of the cat is determined due to the addition of the noise in your brain. There is then no difference between the noiseless case as far as the necessity for a local interaction is concerned (we're replacing explicit communication of the facts with implicit information transfer via noise). If we consider ourselves as programs run by our brains and consider some well defined computational state, look at all the branches where that particular computational state is implemented, then you'll find that it's present in both situations where the information about the cat is different. Hmm. I think there may be a typo here. If the information about the cat is different, it would suggest that the computational state of the
Re: Non-locality and MWI (literature)
On 10/05/2016 2:22 am, Bruno Marchal wrote: On 09 May 2016, at 15:46, Bruce Kellett wrote: On 9/05/2016 10:45 pm, Bruno Marchal wrote: On 09 May 2016, at 04:12, Bruce Kellett wrote: This is the case for the discussion in section 9.1.2 of the paper by Brown and Timpson. Their equation (9) contains all the relevant results that set the universal wave function -- the additional third measurement (or measurement-like interaction) leading to equation (10) is, therefore, irrelevant. All that happens in eq. (10) is an exchange of information -- but it is an exchange of information that is already present in the universal wave function, no new information is created at this point. Just like opening the box on Schrödinger's cat, which is either alive or dead long before, looking changes nothing. Eq. (10) is, similarly, just an interpretive gloss of no fundamental significance. The important point here is that everything is set in the universal wave function /before/ Alice and Bob meet. The relative angle of the respective polarizers is set in the wave function long before the light cones of Alice and Bob overlap, so that relative angle is determined non-locally. The universal wave function is not a local object -- I am not sure what does this mean. The SWE is linear which is a case of extreme locality I would say. Linearity does not entail locality. Where did you get that notion from? If you can show me a linear transformation which emulates something non local (and not just phenomenological), I would be interested. To have the non-locality from Bell, what we are arguing is that you need the collapse, which is not linear. No, you don't need collapse, that is the whole thrust of my argument. I have demonstrated non-locality within the Everettian approach without collapse. Bell's original argument didn't mention collapse, and the argument that his theorem fails because he assumed definite outcomes from measurements is actually without substance: no such assumption is required by Bell. All you have to do to convince yourself of this is to think of my illustration of working in momentum space in order to deal with the superpositions involved in the description of a particle by a wave packet. If there are superpositions involved in the outcome of experiments, it is sufficient for calculational purposes to consider just one typical member of the superposition. The superposition can be recovered later by a convolution integral over the initial distribution. You can study the book by Pour-El, which contributed to my idea that linear transformation preserve local influence. My intution stem from the fact that "linear" is simpler than computable". Of course we use real numbers, and so "computable" itself does not admit standard definition on which everyone agree, so I will not insist on this. the unitary evolution does not have any implicit notion of locality. ? Locality is a human convention, and the universal wave function is under no compulsion to take any notice of human conventions or preferences. The question is only: does Alice's measurement change something instantaneously and physically at a distance? Obviously, this is not a question of convention. No, it is not a convention, and the violation of Bell and similar inequalities shows that such non-local action is present That is what you are asked to justify. And I have done so. -- the measurement at particle 2 is not independent of what happened to particle 1. There is a recent review of Bell non-locality by Brunner et al. (RMP 86 (2014) pp. 419-478) which takes non-locality as an established physical result. This would be the position of most working physicists. Because most working physicist believe there is a unique single physical reality. Argument of majority are not argument at all, also. I see clearly that such action at a distance has to occur in all QM with a physical collapse assumption, as Einstein saw already in 1927 at the Solvay Congress, and EPR-BELL-Bohm made testable. But if the collapse is a first person view entangled with the particle in the singlet state, I don't see any action at a distance occurring, even if it looks like that for the person involved. I don't get your critic of Brown and Timpson (9.1.2 in https://arxiv.org/abs/1501.03521 ). The move from eq. (9) of section 9.1.2 to eq. (10) is unnecessary. In eq (9) all the local measurements are complete; both Alice and Bob have split into A(+) and A(-), and B(+) and B(-), for seeing + or - results respectively. And these measurements were done with particular polarizer orientations, so by the time we can write eq. (9), the relative polarizer orientation, and the set of all possible results, are fixed. Alice and Bob might still be spacelike separated, and Alice may not have been split according to Bob's results, but that does not matter. Everything that is needed for that splitting (if it occurs o
Re: Non-locality and MWI
On 10/05/2016 2:42 am, smitra wrote: On 09-05-2016 07:43, Bruce Kellett wrote: On 9/05/2016 3:17 pm, smitra wrote: On 09-05-2016 03:40, Bruce Kellett wrote: The idea that Alice splits further into different branches according to Bob's results only after their respective light cones overlap is an interpretive gloss on the theory (which, as already pointed out, you do not apply consistently) -- it is not there in the mathematics. Alice and Bob are in the same world even at spacelike separations. This must be the case, or else my feet would be in a different world from my head at every single instant of time. So Bob and Alice separate in the same world. When they perform their measurements there is a Bob in each world created by Alice's results, and an Alice in every world created by Bob's results. The fact that neither Alice nor Bob do not know the other's result does not mean that there are no such results. Are there separate worlds in which these results are combined? It doesn't really matter, because anything that can be seen when information is exchanged is already set: the exchange of information is like opening the box -- the cat is already either alive or dead, opening the box does not change that. So Alice and Bob talking to each other does not change anything either. The results are already present in the universal wave function -- talk of splitting into worlds is irrelevant to the universal wave function and the unitary dynamics. So the fact that A does not know B's results at some time is irrelevant -- the results are already there. The question of who knows what is not a relevant question for the universal wave function. And the universal wave function takes account of the unity of the singlet state and the reality of non-local effects. And this is the core of the disagreement, you say that the results are already there, but in the MWI this is false. What? Are you claiming the the universal wave function -- which contains all possible branches corresponding to all possible outcomes -- does not contain the results? I think what you mean is that you do not know the result (which branch you are on) until you open the box. But that does not mean that you are not on one branch or the other. The death of the cat (if it be so) can be in your past light cone, so the splitting of worlds occasioned by that death has already split you. Your knowledge of this is strictly irrelevant. You can be in a particular world without being aware of it. In Bruno's famous person duplication experiments, you are in either Washington or Moscow before you are necessarily ever aware of which city it is. You make personal knowledge of outcomes far too prominent in your theory; things can actually happen without your being aware of them! While your body does split up, if you don't have the "which branch" information then you are in both branches until that time that you do have this information. Nah. That places far too much emphasis on the conscious mind -- making "what you know" the determiner of physical reality. I think Brent might refer to this as QBism (Quantum Bayesianism). A person is more than just what they happen to be thinking at the moment. If the body participates in the split, the brain also so participates. Instantaneous conscious (or computational) states are transient, and will be influenced by many external influences. Your suggestion, if taken literally, would have us fluctuating uncontrollably between one world or many. Not a good idea. I think we have to gives some significance to the objective state of the wave function. That is what is determined by unitary evolution; what we think about it is irreducibly secondary. If we consider ourselves as programs run by our brains and consider some well defined computational state, look at all the branches where that particular computational state is implemented, then you'll find that it's present in both situations where the information about the cat is different. Hmm. I think there may be a typo here. If the information about the cat is different, it would suggest that the computational state of the brain is different -- information is reflected in the computational state, after all. If it is not, it is just noise, not information. By relying so completely on what we know, or our conscious state, I think you push computationalism beyond its reasonable limits. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 5/9/2016 9:26 AM, smitra wrote: On 09-05-2016 07:37, Brent Meeker wrote: On 5/8/2016 10:17 PM, smitra wrote: On 09-05-2016 03:40, Bruce Kellett wrote: On 9/05/2016 2:58 am, smitra wrote: On 08-05-2016 01:52, Bruce Kellett wrote: The set-up of the experiment belies the second part of your comment. The information about the angles was not in the initial state. Sure, the dynamics of the interaction between the particles and the polarizer is local, and the polarizer angle is also set locally, but the entangled state that interacts with the polarizer is itself not local -- it is spread out in space. It is because the original entangled state is spread out that the polarizers at each end react in tandem -- giving rise to the non-locality. Interactions in this are all local, the non-locality arises from the fact that the singlet state itself is not localized. Yes, but that's again a trivial non-local effect as the entangled spins were created locally in the past. In the MWI this only gives rise to non-local effects that are trivial common cause effects, unlike in single World interpretations. It is not a common cause effect. The singlet state is, but the polarizer setting of A and B are independently and freely chosen after the particles are widely separated. There is no common cause for this. Alternatively, you can let Alice and Bob do additional measurements of quantum systems and then set the polarizer settings according to what they find. In that case the information about the settings was not put in the initial state but it then arises out of the dynamics. However, you then get a superposition of all possibilities, Superposition of all which possibilities? I imagine that what you are saying is that if the setting is chosen according to the outcome of some other quantum event, then all possible outcomes of that event are realized in different branches of a superposition, or in different worlds. This does not actually help you. Remember that each of the worlds in which these different settings obtain also contains a copy of the same particle that is part of the entangled pair (Alice measured the other part). So in each branch of your new superposition, the same state is measured in some direction. Whichever branch Bob then finds himself in, he still has eventually to communicate with Alice. And all the Bob's in this picture have their own particular theta and |+> or |-> result. The multiplication of possibilities for Bob has not removed the problem of how this theta is determined for each copy. The essential non-locality remains. The relative angle theta is not determined for each copy separately, each branch of Alice contains all the branches of Bob where Bob chooses some angle and vice versa. The relative angle is only going to be determined later when Alice and Bob communicate, it's only then that Alice and Bob get localized into branches where the relative angle is determined. This additional superposition that you are invoking is actually irrelevant. It is quite common in physics to deal with such superpositions by considering just one typical member of the superposition and performing the calculation for that particular case. The general superposed case can be added back later if required, but it does not add anything new. The paradigm illustration of this is in particle physics. Because of the uncertainty principle, a particle is effectively never in an eigenstate of either position or momentum -- it is typically a wave packet, in which the spreads over various position and momentum eigenstates are related by a Fourier transform. In order to calculate scattering probability, for example, one works in momentum space by choice since conservation of energy and momentum give considerable kinematic simplifications. But one does not have to do the calculation for every momentum in the superposition constituting the original wave packet: one chooses a typical momentum and works with that eigenstate alone. If one wants to recreate the packet effect, a simple integration over the momentum distribution is all that is required. So introducing a multiplicity of copies of Bob, each with its own measurement angle, is a red herring. One need consider only one typical orientation, because in the final analysis, there is only one polarizer setting for Bob that has to be compared with Alice's polarizer setting. The important point remains the same -- the settings for both Alice and Bob are chose and set classically by decoherence long before they ever meet up again. So the relative angle is not determined only when their future light cones overlap -- that relative angle was set when they were at a spacelike separation. it's only when you choose to look at the sector where the settings were the same or opposite settings were chosen that you get the reduction of the number of states. But that sector is defined by what happens on both sides, so there is no strange non-loc
R: Re: R: Re: Non-locality and MWI
Messaggio originale Da: Brent Meeker Data: 09/05/2016 18.50 A: Ogg: Re: R: Re: Non-locality and MWI On 5/9/2016 12:52 AM, 'scerir' via Everything List wrote: Saibal Mitra: And this is the core of the disagreement, you say that the results are already there, but in the MWI this is false. In the MWI the cat is not either dead or alive before you open the box, the superposition has become entangled with the environment, but both branches are relevant until you get to know the result. It seems (to me) interesting this quote from Nicolas Gisin "Against Many- Worlds", ch. 4 of the paper ' Are There Quantum Effects Coming from Outside Space-time? Nonlocality, free will and "no many-worlds" ' http://arxiv.org/pdf/1011.3440.pdf "On the contrary, I do not see any explanatory power in the many worlds: it seems to be made just to prevent one from asking (possibly provocative) questions. Moreover, it has built in it the impossibility of any test: all its predictions are identical to those of quantum theory. For me, it looks like "cushion for laziness" (un coussin de paresse in French). It avoids the otherwise puzzling question of, "When does the wave function collapse? Why is a measurement different from other physical interactions?" QBism provides one answer, but at the cost of losing a kind of absolute objectivity. Other solutions, like Bohm and GRW, postulate truly different physics that produce collapse. Yes. And I was not aware of the MIW interpretation !"In the Everett or MW interpretation, the `worlds' are orthogonal components of a universal wave function . The particular decomposition at any time, and the identity of worlds through time is argued to be defined (at least well-enough for practical purposes) by the quantum dynamics which generates essentially independent evolution of these quasiclassical worlds into the future (a phenomenon called effective decoherence). The inherent fuzziness of Everettian worlds is in contrast to the corresponding concepts in the MIW [Many Interacting classical Worlds] approach, of a well-defined group of deterministically-evolving configurations. In the MW interpretation it is meaningless to ask exactly how many worlds there are at a given time, or exactly when a branching event into subcomponents occurs, leading to criticisms that there is no precise ontology Another di ffcult issue is that worlds are not equally `real' in the MW interpretation, but are `weighted' by the modulus squared of the corresponding superposition coeffi cients. As noted above, in the MIW approach all worlds are equally weighted, so that Laplace's theory of probability is su fficient to account for our experience and expectations." https://arxiv.org/pdf/1402.6144v4.pdf And there is a second, decisive, reason to reject the many-worlds view: it leaves no space for free will." That's a silly reason. Daniel Dennett, in his book Elbow Room, explains that even Laplacian determinism leaves us all the free will worth having. Brent -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI
On 09-05-2016 09:52, 'scerir' via Everything List wrote: Saibal Mitra: And this is the core of the disagreement, you say that the results are already there, but in the MWI this is false. In the MWI the cat is not either dead or alive before you open the box, the superposition has become entangled with the environment, but both branches are relevant until you get to know the result. It seems (to me) interesting this quote from Nicolas Gisin "Against Many- Worlds", ch. 4 of the paper ' Are There Quantum Effects Coming from Outside Space-time? Nonlocality, free will and "no many-worlds" ' http://arxiv.org/pdf/1011.3440.pdf "On the contrary, I do not see any explanatory power in the many worlds: it seems to be made just to prevent one from asking (possibly provocative) questions. Moreover, it has built in it the impossibility of any test: all its predictions are identical to those of quantum theory. For me, it looks like "cushion for laziness" (un coussin de paresse in French). And there is a second, decisive, reason to reject the many-worlds view: it leaves no space for free will." That's a philosophical argument against MWI. I.m.o. it is important is to work within some given framework when discussing issues within that framework. It's similar to how the old discussions about Maxwell's Demon did not yield the deep insight about the relevance of information theory in thermodynamics and statistical physics. Strange ideas can lead people to rail against it and raise objections on e.g. practical grounds that may have some merit but they distract from the fundamental issue raised by the thought experiment. One then doesn't follow through the argument to its logical end. Saibal -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI
On 5/9/2016 12:52 AM, 'scerir' via Everything List wrote: Saibal Mitra: And this is the core of the disagreement, you say that the results are already there, but in the MWI this is false. In the MWI the cat is not either dead or alive before you open the box, the superposition has become entangled with the environment, but both branches are relevant until you get to know the result. It seems (to me) interesting this quote from Nicolas Gisin "Against Many- Worlds", ch. 4 of the paper ' Are There Quantum Effects Coming from Outside Space-time? Nonlocality, free will and "no many-worlds" ' http://arxiv.org/pdf/1011.3440.pdf "On the contrary, I do not see any explanatory power in the many worlds: it seems to be made just to prevent one from asking (possibly provocative) questions. Moreover, it has built in it the impossibility of any test: all its predictions are identical to those of quantum theory. For me, it looks like "cushion for laziness" (un coussin de paresse in French). It avoids the otherwise puzzling question of, "When does the wave function collapse? Why is a measurement different from other physical interactions?" QBism provides one answer, but at the cost of losing a kind of absolute objectivity. Other solutions, like Bohm and GRW, postulate truly different physics that produce collapse. And there is a second, decisive, reason to reject the many-worlds view: it leaves no space for free will." That's a silly reason. Daniel Dennett, in his book /Elbow Room/, explains that even Laplacian determinism leaves us all the free will worth having. Brent -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 09-05-2016 07:43, Bruce Kellett wrote: On 9/05/2016 3:17 pm, smitra wrote: On 09-05-2016 03:40, Bruce Kellett wrote: The idea that Alice splits further into different branches according to Bob's results only after their respective light cones overlap is an interpretive gloss on the theory (which, as already pointed out, you do not apply consistently) -- it is not there in the mathematics. Alice and Bob are in the same world even at spacelike separations. This must be the case, or else my feet would be in a different world from my head at every single instant of time. So Bob and Alice separate in the same world. When they perform their measurements there is a Bob in each world created by Alice's results, and an Alice in every world created by Bob's results. The fact that neither Alice nor Bob do not know the other's result does not mean that there are no such results. Are there separate worlds in which these results are combined? It doesn't really matter, because anything that can be seen when information is exchanged is already set: the exchange of information is like opening the box -- the cat is already either alive or dead, opening the box does not change that. So Alice and Bob talking to each other does not change anything either. The results are already present in the universal wave function -- talk of splitting into worlds is irrelevant to the universal wave function and the unitary dynamics. So the fact that A does not know B's results at some time is irrelevant -- the results are already there. The question of who knows what is not a relevant question for the universal wave function. And the universal wave function takes account of the unity of the singlet state and the reality of non-local effects. And this is the core of the disagreement, you say that the results are already there, but in the MWI this is false. What? Are you claiming the the universal wave function -- which contains all possible branches corresponding to all possible outcomes -- does not contain the results? I think what you mean is that you do not know the result (which branch you are on) until you open the box. But that does not mean that you are not on one branch or the other. The death of the cat (if it be so) can be in your past light cone, so the splitting of worlds occasioned by that death has already split you. Your knowledge of this is strictly irrelevant. You can be in a particular world without being aware of it. In Bruno's famous person duplication experiments, you are in either Washington or Moscow before you are necessarily ever aware of which city it is. You make personal knowledge of outcomes far too prominent in your theory; things can actually happen without your being aware of them! While your body does split up, if you don't have the "which branch" information then you are in both branches until that time that you do have this information. If we consider ourselves as programs run by our brains and consider some well defined computational state, look at all the branches where that particular computational state is implemented, then you'll find that it's present in both situations where the information about the cat is different. Saibal -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 09-05-2016 07:37, Brent Meeker wrote: On 5/8/2016 10:17 PM, smitra wrote: On 09-05-2016 03:40, Bruce Kellett wrote: On 9/05/2016 2:58 am, smitra wrote: On 08-05-2016 01:52, Bruce Kellett wrote: The set-up of the experiment belies the second part of your comment. The information about the angles was not in the initial state. Sure, the dynamics of the interaction between the particles and the polarizer is local, and the polarizer angle is also set locally, but the entangled state that interacts with the polarizer is itself not local -- it is spread out in space. It is because the original entangled state is spread out that the polarizers at each end react in tandem -- giving rise to the non-locality. Interactions in this are all local, the non-locality arises from the fact that the singlet state itself is not localized. Yes, but that's again a trivial non-local effect as the entangled spins were created locally in the past. In the MWI this only gives rise to non-local effects that are trivial common cause effects, unlike in single World interpretations. It is not a common cause effect. The singlet state is, but the polarizer setting of A and B are independently and freely chosen after the particles are widely separated. There is no common cause for this. Alternatively, you can let Alice and Bob do additional measurements of quantum systems and then set the polarizer settings according to what they find. In that case the information about the settings was not put in the initial state but it then arises out of the dynamics. However, you then get a superposition of all possibilities, Superposition of all which possibilities? I imagine that what you are saying is that if the setting is chosen according to the outcome of some other quantum event, then all possible outcomes of that event are realized in different branches of a superposition, or in different worlds. This does not actually help you. Remember that each of the worlds in which these different settings obtain also contains a copy of the same particle that is part of the entangled pair (Alice measured the other part). So in each branch of your new superposition, the same state is measured in some direction. Whichever branch Bob then finds himself in, he still has eventually to communicate with Alice. And all the Bob's in this picture have their own particular theta and |+> or |-> result. The multiplication of possibilities for Bob has not removed the problem of how this theta is determined for each copy. The essential non-locality remains. The relative angle theta is not determined for each copy separately, each branch of Alice contains all the branches of Bob where Bob chooses some angle and vice versa. The relative angle is only going to be determined later when Alice and Bob communicate, it's only then that Alice and Bob get localized into branches where the relative angle is determined. This additional superposition that you are invoking is actually irrelevant. It is quite common in physics to deal with such superpositions by considering just one typical member of the superposition and performing the calculation for that particular case. The general superposed case can be added back later if required, but it does not add anything new. The paradigm illustration of this is in particle physics. Because of the uncertainty principle, a particle is effectively never in an eigenstate of either position or momentum -- it is typically a wave packet, in which the spreads over various position and momentum eigenstates are related by a Fourier transform. In order to calculate scattering probability, for example, one works in momentum space by choice since conservation of energy and momentum give considerable kinematic simplifications. But one does not have to do the calculation for every momentum in the superposition constituting the original wave packet: one chooses a typical momentum and works with that eigenstate alone. If one wants to recreate the packet effect, a simple integration over the momentum distribution is all that is required. So introducing a multiplicity of copies of Bob, each with its own measurement angle, is a red herring. One need consider only one typical orientation, because in the final analysis, there is only one polarizer setting for Bob that has to be compared with Alice's polarizer setting. The important point remains the same -- the settings for both Alice and Bob are chose and set classically by decoherence long before they ever meet up again. So the relative angle is not determined only when their future light cones overlap -- that relative angle was set when they were at a spacelike separation. it's only when you choose to look at the sector where the settings were the same or opposite settings were chosen that you get the reduction of the number of states. But that sector is defined by what happens on both sides, so there is no strange non-local effect here th
Re: Non-locality and MWI (literature)
On 09 May 2016, at 15:46, Bruce Kellett wrote: On 9/05/2016 10:45 pm, Bruno Marchal wrote: On 09 May 2016, at 04:12, Bruce Kellett wrote: On 9/05/2016 1:39 am, Bruno Marchal wrote: Thanks Scerir. Very interesting. On 08 May 2016, at 09:58, 'scerir' via Everything List wrote: https://arxiv.org/abs/1501.03521 'Bell on Bell's theorem: The changing face of nonlocality' Authors: Harvey R. Brown, Christopher G. Timpson there are several interesting points here ch. 9 - Locality in the Everett picture ch. 9.1 EPR and Bell correlations in the Everettian setting Nice. I think that what we are trying to explain to Bruce is well summed up in their section 9.1.2 (the Everett description of the singlet state, case of non-align polarizer). I have already discussed this in my reply to Saibal. The basic point I would make again is that the splitting of the universal wave function into separate "worlds" is an interpretive gloss that does not actually alter anything in the theory. As long as you don't separate them too much, as the wave describe a pure state remaining pure all the time, the "world" are the phenomenological views as seen by each doppelgangers involved. If not, you lose the possible interferences in principle possible by quantum memory erasure. Quantum erasure is possible only in limited, tightly controlled circumstances. Generally, decoherence into many environmental degrees of freedom is irreversible FAPP. Absolutely, but the arguments here is not concerned with the PP (the Practical Purpose in the "FAPP" (For all Parctical purposes). Furthermore, 'who knows what about whatever' is also an irrelevance as far as the universal wave function is concerned. If you are going to work in the many worlds paradigm, then everything ultimately stems from the unitary evolution of the universal wave function -- all else is just interpretive gloss, of no fundamental significance. This is the case for the discussion in section 9.1.2 of the paper by Brown and Timpson. Their equation (9) contains all the relevant results that set the universal wave function -- the additional third measurement (or measurement-like interaction) leading to equation (10) is, therefore, irrelevant. All that happens in eq. (10) is an exchange of information -- but it is an exchange of information that is already present in the universal wave function, no new information is created at this point. Just like opening the box on Schrödinger's cat, which is either alive or dead long before, looking changes nothing. Eq. (10) is, similarly, just an interpretive gloss of no fundamental significance. The important point here is that everything is set in the universal wave function before Alice and Bob meet. The relative angle of the respective polarizers is set in the wave function long before the light cones of Alice and Bob overlap, so that relative angle is determined non-locally. The universal wave function is not a local object -- I am not sure what does this mean. The SWE is linear which is a case of extreme locality I would say. Linearity does not entail locality. Where did you get that notion from? If you can show me a linear transformation which emulates something non local (and not just phenomenological), I would be interested. To have the non-locality from Bell, what we are arguing is that you need the collapse, which is not linear. You can study the book by Pour-El, which contributed to my idea that linear transformation preserve local influence. My intution stem from the fact that "linear" is simpler than computable". Of course we use real numbers, and so "computable" itself does not admit standard definition on which everyone agree, so I will not insist on this. the unitary evolution does not have any implicit notion of locality. ? Locality is a human convention, and the universal wave function is under no compulsion to take any notice of human conventions or preferences. The question is only: does Alice's measurement change something instantaneously and physically at a distance? Obviously, this is not a question of convention. No, it is not a convention, and the violation of Bell and similar inequalities shows that such non-local action is present That is what you are asked to justify. -- the measurement at particle 2 is not independent of what happened to particle 1. There is a recent review of Bell non-locality by Brunner et al. (RMP 86 (2014) pp. 419-478) which takes non-locality as an established physical result. This would be the position of most working physicists. Because most working physicist believe there is a unique single physical reality. Argument of majority are not argument at all, also. I see clearly that such action at a distance has to occur in all QM with a physical collapse assumption, as Einstein saw already in 1927 at the Solvay Congress, and
Re: Non-locality and MWI (literature)
On 9/05/2016 10:45 pm, Bruno Marchal wrote: On 09 May 2016, at 04:12, Bruce Kellett wrote: On 9/05/2016 1:39 am, Bruno Marchal wrote: Thanks Scerir. Very interesting. On 08 May 2016, at 09:58, 'scerir' via Everything List wrote: https://arxiv.org/abs/1501.03521 'Bell on Bell's theorem: The changing face of nonlocality' Authors: Harvey R. Brown, Christopher G. Timpson there are several interesting points here ch. 9 - Locality in the Everett picture ch. 9.1 EPR and Bell correlations in the Everettian setting Nice. I think that what we are trying to explain to Bruce is well summed up in their section 9.1.2 (the Everett description of the singlet state, case of non-align polarizer). I have already discussed this in my reply to Saibal. The basic point I would make again is that the splitting of the universal wave function into separate "worlds" is an interpretive gloss that does not actually alter anything in the theory. As long as you don't separate them too much, as the wave describe a pure state remaining pure all the time, the "world" are the phenomenological views as seen by each doppelgangers involved. If not, you lose the possible interferences in principle possible by quantum memory erasure. Quantum erasure is possible only in limited, tightly controlled circumstances. Generally, decoherence into many environmental degrees of freedom is irreversible FAPP. Furthermore, 'who knows what about whatever' is also an irrelevance as far as the universal wave function is concerned. If you are going to work in the many worlds paradigm, then everything ultimately stems from the unitary evolution of the universal wave function -- all else is just interpretive gloss, of no fundamental significance. This is the case for the discussion in section 9.1.2 of the paper by Brown and Timpson. Their equation (9) contains all the relevant results that set the universal wave function -- the additional third measurement (or measurement-like interaction) leading to equation (10) is, therefore, irrelevant. All that happens in eq. (10) is an exchange of information -- but it is an exchange of information that is already present in the universal wave function, no new information is created at this point. Just like opening the box on Schrödinger's cat, which is either alive or dead long before, looking changes nothing. Eq. (10) is, similarly, just an interpretive gloss of no fundamental significance. The important point here is that everything is set in the universal wave function /before/ Alice and Bob meet. The relative angle of the respective polarizers is set in the wave function long before the light cones of Alice and Bob overlap, so that relative angle is determined non-locally. The universal wave function is not a local object -- I am not sure what does this mean. The SWE is linear which is a case of extreme locality I would say. Linearity does not entail locality. Where did you get that notion from? the unitary evolution does not have any implicit notion of locality. ? Locality is a human convention, and the universal wave function is under no compulsion to take any notice of human conventions or preferences. The question is only: does Alice's measurement change something instantaneously and physically at a distance? Obviously, this is not a question of convention. No, it is not a convention, and the violation of Bell and similar inequalities shows that such non-local action is present -- the measurement at particle 2 is not independent of what happened to particle 1. There is a recent review of Bell non-locality by Brunner et al. (RMP 86 (2014) pp. 419-478) which takes non-locality as an established physical result. This would be the position of most working physicists. I see clearly that such action at a distance has to occur in all QM with a physical collapse assumption, as Einstein saw already in 1927 at the Solvay Congress, and EPR-BELL-Bohm made testable. But if the collapse is a first person view entangled with the particle in the singlet state, I don't see any action at a distance occurring, even if it looks like that for the person involved. I don't get your critic of Brown and Timpson (9.1.2 in https://arxiv.org/abs/1501.03521 ). The move from eq. (9) of section 9.1.2 to eq. (10) is unnecessary. In eq (9) all the local measurements are complete; both Alice and Bob have split into A(+) and A(-), and B(+) and B(-), for seeing + or - results respectively. And these measurements were done with particular polarizer orientations, so by the time we can write eq. (9), the relative polarizer orientation, and the set of all possible results, are fixed. Alice and Bob might still be spacelike separated, and Alice may not have been split according to Bob's results, but that does not matter. Everything that is needed for that splitting (if it occurs only after the light cones intersect) is in place -- nothing new is added when th
Re: Non-locality and MWI (literature)
On 09 May 2016, at 04:12, Bruce Kellett wrote: On 9/05/2016 1:39 am, Bruno Marchal wrote: Thanks Scerir. Very interesting. On 08 May 2016, at 09:58, 'scerir' via Everything List wrote: https://arxiv.org/abs/1501.03521 'Bell on Bell's theorem: The changing face of nonlocality' Authors: Harvey R. Brown, Christopher G. Timpson there are several interesting points here ch. 9 - Locality in the Everett picture ch. 9.1 EPR and Bell correlations in the Everettian setting Nice. I think that what we are trying to explain to Bruce is well summed up in their section 9.1.2 (the Everett description of the singlet state, case of non-align polarizer). I have already discussed this in my reply to Saibal. The basic point I would make again is that the splitting of the universal wave function into separate "worlds" is an interpretive gloss that does not actually alter anything in the theory. As long as you don't separate them too much, as the wave describe a pure state remaining pure all the time, the "world" are the phenomenological views as seen by each doppelgangers involved. If not, you lose the possible interferences in principle possible by quantum memory erasure. Furthermore, 'who knows what about whatever' is also an irrelevance as far as the universal wave function is concerned. If you are going to work in the many worlds paradigm, then everything ultimately stems from the unitary evolution of the universal wave function -- all else is just interpretive gloss, of no fundamental significance. This is the case for the discussion in section 9.1.2 of the paper by Brown and Timpson. Their equation (9) contains all the relevant results that set the universal wave function -- the additional third measurement (or measurement-like interaction) leading to equation (10) is, therefore, irrelevant. All that happens in eq. (10) is an exchange of information -- but it is an exchange of information that is already present in the universal wave function, no new information is created at this point. Just like opening the box on Schrödinger's cat, which is either alive or dead long before, looking changes nothing. Eq. (10) is, similarly, just an interpretive gloss of no fundamental significance. The important point here is that everything is set in the universal wave function before Alice and Bob meet. The relative angle of the respective polarizers is set in the wave function long before the light cones of Alice and Bob overlap, so that relative angle is determined non- locally. The universal wave function is not a local object -- I am not sure what does this mean. The SWE is linear which is a case of extreme locality I would say. the unitary evolution does not have any implicit notion of locality. ? Locality is a human convention, and the universal wave function is under no compulsion to take any notice of human conventions or preferences. The question is only: does Alice's measurement change something instantaneously and physically at a distance? Obviously, this is not a question of convention. I see clearly that such action at a distance has to occur in all QM with a physical collapse assumption, as Einstein saw already in 1927 at the Solvay Congress, and EPR-BELL-Bohm made testable. But if the collapse is a first person view entangled with the particle in the singlet state, I don't see any action at a distance occurring, even if it looks like that for the person involved. I don't get your critic of Brown and Timpson (9.1.2 in https://arxiv.org/abs/1501.03521 ). Brown and Simpson are close to my feeling (say), which is that Bell's inequality violation testing does not test locality, but the MWI itself. Bruno Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
Oops, Sorry Bruce, that following mail might have been resent a second tie by error. May be you can check, my server seems to have a queer behavior. Bruno On 09 May 2016, at 14:14, Bruno Marchal wrote: On 30 Apr 2016, at 02:32, Bruce Kellett wrote: On 29/04/2016 9:09 pm, Bruno Marchal wrote: On 28 Apr 2016, at 03:33, Bruce Kellett wrote: On 27/04/2016 4:57 pm, Bruno Marchal wrote: On 27 Apr 2016, at 06:49, Bruce Kellett wrote: On 27/04/2016 1:51 pm, Brent Meeker wrote: That's pretty much the many-universes model that Bruno proposes. But it's non-local in the sense that the "matching scheme" must take account of which measurements are compatible, i.e. it "knows" the results even while they are spacelike separated. Exactly, the model assumes the results it is trying to get. It is not a local physical model because the statistics do not originate locally. The statistic did originate locally. Alice and Bob did prepare the singlet state locally, and then travel away. That is not strictly correct. The singlet state is conventionally prepared centrally between A and B so that the measurements can be made at spacelike separation. That would not be possible if A and B jointly prepare the state then move away. The measurement? OK. Not the preparation. They are in infinitely many worlds, and in each with opposite spin. There are only two possible spin states for each -- so there are really only two distinct possible worlds. Multiplying copies of these two does not seem to accomplish much. There is an infinity of possible states for each. There is an infinity of possible distinct possible worlds. In each one A's and B's particle spin are opposite/correlated, but neither Alice nor Bob can know which one. I think you are getting confused by the basis problem again. I think you misinterpret the MWI? It might be related with your problem with the first person indeterminacy in self-multiplication, and your abstraction from the fact that the singlet state has basically the same form in all base. Once Bob is in a separate light cone, it is isolated from Alice, but the singlet state justifies why the infinitely many Alices it describes will be correlated with the Bob they are arble to talk with. The cos^2(theta) is given by the math of the 1/sqrt(2)AB(I+>I-> - I->I+>)) = 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+>. With your explanation to Jesse, I keep the feeling that you talk like if Alice or Bob reduce the wave after their measurement, but they just localize themselves in the relative branches. Certainly, the cos^2(theta/2) comes from applying the standard quantum rules to the singlet state |psi> = (|+>|-> - |->|+>)/sqrt(2) (adding AB to this state adds nothing). We need them to get all the statistics correct. I think it would be instructive to actually go through the usual quantum derivation of the correlations because what you call "reducing the wave after the measurement" is actually the result of applying the standard quantum rules. It has nothing to do with so-called 'collapse' interpretations: it is simply in the theory. Well, either the meaurement give specific outcome, or, if there is no physical collapse it is only an entanglement between A (or B) with the singlet state. That is why A and B are needed in the derivation. A measurement results in an entanglement between the state and the observer. But in order for the observer to see only one result (and not a superposition) you need the projection postulate. That is decoherence, not a rejection of many worlds. You need only to look at the first person views of the relative persons in the superposition states, they are infinite in a relative proportion given by the Born rules. Quantum rules for measurement say that the initial state can be expanded in the basis corresponding to the particular measurement in question (contextuality). That is what the state |psi> above is -- the quantum expansion of the singlet state in the basis in which say Alice is doing her measurement. OK, but that state does not represent two possible worlds. It looks like that for Alice because she has decided to make the measurement "in that base", but, as we know, the correlation does not depend on the choice of Alice's measurement. She will just entangled herself with the singlet state, whatever the base or measuring apparatus is. Quantum rules then say that the result of the measurement (after decoherence has fully operated) Decoherence is only the contagion of the superposition to the observer and/or his/her environment. It does not lead to a classical universe. That is only what the infinitely many Alice will phenomenologivally realize. Decoherence is the basis for the (apparent) emergence of the classical from the quantum. Decoherence allows coarse-graining, partial tracing over environmental variables, and the other things
Re: Non-locality and MWI
On 30 Apr 2016, at 02:32, Bruce Kellett wrote: On 29/04/2016 9:09 pm, Bruno Marchal wrote: On 28 Apr 2016, at 03:33, Bruce Kellett wrote: On 27/04/2016 4:57 pm, Bruno Marchal wrote: On 27 Apr 2016, at 06:49, Bruce Kellett wrote: On 27/04/2016 1:51 pm, Brent Meeker wrote: That's pretty much the many-universes model that Bruno proposes. But it's non-local in the sense that the "matching scheme" must take account of which measurements are compatible, i.e. it "knows" the results even while they are spacelike separated. Exactly, the model assumes the results it is trying to get. It is not a local physical model because the statistics do not originate locally. The statistic did originate locally. Alice and Bob did prepare the singlet state locally, and then travel away. That is not strictly correct. The singlet state is conventionally prepared centrally between A and B so that the measurements can be made at spacelike separation. That would not be possible if A and B jointly prepare the state then move away. The measurement? OK. Not the preparation. They are in infinitely many worlds, and in each with opposite spin. There are only two possible spin states for each -- so there are really only two distinct possible worlds. Multiplying copies of these two does not seem to accomplish much. There is an infinity of possible states for each. There is an infinity of possible distinct possible worlds. In each one A's and B's particle spin are opposite/correlated, but neither Alice nor Bob can know which one. I think you are getting confused by the basis problem again. I think you misinterpret the MWI? It might be related with your problem with the first person indeterminacy in self-multiplication, and your abstraction from the fact that the singlet state has basically the same form in all base. Once Bob is in a separate light cone, it is isolated from Alice, but the singlet state justifies why the infinitely many Alices it describes will be correlated with the Bob they are arble to talk with. The cos^2(theta) is given by the math of the 1/sqrt(2)AB(I+>I-> - I->I+>)) = 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+>. With your explanation to Jesse, I keep the feeling that you talk like if Alice or Bob reduce the wave after their measurement, but they just localize themselves in the relative branches. Certainly, the cos^2(theta/2) comes from applying the standard quantum rules to the singlet state |psi> = (|+>|-> - |->|+>)/sqrt(2) (adding AB to this state adds nothing). We need them to get all the statistics correct. I think it would be instructive to actually go through the usual quantum derivation of the correlations because what you call "reducing the wave after the measurement" is actually the result of applying the standard quantum rules. It has nothing to do with so-called 'collapse' interpretations: it is simply in the theory. Well, either the meaurement give specific outcome, or, if there is no physical collapse it is only an entanglement between A (or B) with the singlet state. That is why A and B are needed in the derivation. A measurement results in an entanglement between the state and the observer. But in order for the observer to see only one result (and not a superposition) you need the projection postulate. That is decoherence, not a rejection of many worlds. You need only to look at the first person views of the relative persons in the superposition states, they are infinite in a relative proportion given by the Born rules. Quantum rules for measurement say that the initial state can be expanded in the basis corresponding to the particular measurement in question (contextuality). That is what the state |psi> above is -- the quantum expansion of the singlet state in the basis in which say Alice is doing her measurement. OK, but that state does not represent two possible worlds. It looks like that for Alice because she has decided to make the measurement "in that base", but, as we know, the correlation does not depend on the choice of Alice's measurement. She will just entangled herself with the singlet state, whatever the base or measuring apparatus is. Quantum rules then say that the result of the measurement (after decoherence has fully operated) Decoherence is only the contagion of the superposition to the observer and/or his/her environment. It does not lead to a classical universe. That is only what the infinitely many Alice will phenomenologivally realize. Decoherence is the basis for the (apparent) emergence of the classical from the quantum. Decoherence allows coarse-graining, partial tracing over environmental variables, and the other things that enable us to get definite experimental results. But is only relative first person plural views. No classical universe needs to ever be infinitely singularize? Neither with QM (without collapse) nor w
R: Re: Non-locality and MWI
Saibal Mitra: > And this is the core of the disagreement, you say that the results are > already there, but in the MWI this is false. In the MWI the cat is not > either dead or alive before you open the box, the superposition has > become entangled with the environment, but both branches are relevant > until you get to know the result. It seems (to me) interesting this quote from Nicolas Gisin "Against Many- Worlds", ch. 4 of the paper ' Are There Quantum Effects Coming from Outside Space-time? Nonlocality, free will and "no many-worlds" ' http://arxiv.org/pdf/1011.3440.pdf "On the contrary, I do not see any explanatory power in the many worlds: it seems to be made just to prevent one from asking (possibly provocative) questions. Moreover, it has built in it the impossibility of any test: all its predictions are identical to those of quantum theory. For me, it looks like "cushion for laziness" (un coussin de paresse in French). And there is a second, decisive, reason to reject the many-worlds view: it leaves no space for free will." -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 9/05/2016 3:17 pm, smitra wrote: On 09-05-2016 03:40, Bruce Kellett wrote: The idea that Alice splits further into different branches according to Bob's results only after their respective light cones overlap is an interpretive gloss on the theory (which, as already pointed out, you do not apply consistently) -- it is not there in the mathematics. Alice and Bob are in the same world even at spacelike separations. This must be the case, or else my feet would be in a different world from my head at every single instant of time. So Bob and Alice separate in the same world. When they perform their measurements there is a Bob in each world created by Alice's results, and an Alice in every world created by Bob's results. The fact that neither Alice nor Bob do not know the other's result does not mean that there are no such results. Are there separate worlds in which these results are combined? It doesn't really matter, because anything that can be seen when information is exchanged is already set: the exchange of information is like opening the box -- the cat is already either alive or dead, opening the box does not change that. So Alice and Bob talking to each other does not change anything either. The results are already present in the universal wave function -- talk of splitting into worlds is irrelevant to the universal wave function and the unitary dynamics. So the fact that A does not know B's results at some time is irrelevant -- the results are already there. The question of who knows what is not a relevant question for the universal wave function. And the universal wave function takes account of the unity of the singlet state and the reality of non-local effects. And this is the core of the disagreement, you say that the results are already there, but in the MWI this is false. What? Are you claiming the the universal wave function -- which contains all possible branches corresponding to all possible outcomes -- does not contain the results? I think what you mean is that you do not know the result (which branch you are on) until you open the box. But that does not mean that you are not on one branch or the other. The death of the cat (if it be so) can be in your past light cone, so the splitting of worlds occasioned by that death has already split you. Your knowledge of this is strictly irrelevant. You can be in a particular world without being aware of it. In Bruno's famous person duplication experiments, you are in either Washington or Moscow before you are necessarily ever aware of which city it is. You make personal knowledge of outcomes far too prominent in your theory; things can actually happen without your being aware of them! Bruce In the MWI the cat is not either dead or alive before you open the box, the superposition has become entangled with the environment, but both branches are relevant until you get to know the result. If you find a dead cat then that does not mean that this outcome was predetermined. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 5/8/2016 10:17 PM, smitra wrote: On 09-05-2016 03:40, Bruce Kellett wrote: On 9/05/2016 2:58 am, smitra wrote: On 08-05-2016 01:52, Bruce Kellett wrote: The set-up of the experiment belies the second part of your comment. The information about the angles was not in the initial state. Sure, the dynamics of the interaction between the particles and the polarizer is local, and the polarizer angle is also set locally, but the entangled state that interacts with the polarizer is itself not local -- it is spread out in space. It is because the original entangled state is spread out that the polarizers at each end react in tandem -- giving rise to the non-locality. Interactions in this are all local, the non-locality arises from the fact that the singlet state itself is not localized. Yes, but that's again a trivial non-local effect as the entangled spins were created locally in the past. In the MWI this only gives rise to non-local effects that are trivial common cause effects, unlike in single World interpretations. It is not a common cause effect. The singlet state is, but the polarizer setting of A and B are independently and freely chosen after the particles are widely separated. There is no common cause for this. Alternatively, you can let Alice and Bob do additional measurements of quantum systems and then set the polarizer settings according to what they find. In that case the information about the settings was not put in the initial state but it then arises out of the dynamics. However, you then get a superposition of all possibilities, Superposition of all which possibilities? I imagine that what you are saying is that if the setting is chosen according to the outcome of some other quantum event, then all possible outcomes of that event are realized in different branches of a superposition, or in different worlds. This does not actually help you. Remember that each of the worlds in which these different settings obtain also contains a copy of the same particle that is part of the entangled pair (Alice measured the other part). So in each branch of your new superposition, the same state is measured in some direction. Whichever branch Bob then finds himself in, he still has eventually to communicate with Alice. And all the Bob's in this picture have their own particular theta and |+> or |-> result. The multiplication of possibilities for Bob has not removed the problem of how this theta is determined for each copy. The essential non-locality remains. The relative angle theta is not determined for each copy separately, each branch of Alice contains all the branches of Bob where Bob chooses some angle and vice versa. The relative angle is only going to be determined later when Alice and Bob communicate, it's only then that Alice and Bob get localized into branches where the relative angle is determined. This additional superposition that you are invoking is actually irrelevant. It is quite common in physics to deal with such superpositions by considering just one typical member of the superposition and performing the calculation for that particular case. The general superposed case can be added back later if required, but it does not add anything new. The paradigm illustration of this is in particle physics. Because of the uncertainty principle, a particle is effectively never in an eigenstate of either position or momentum -- it is typically a wave packet, in which the spreads over various position and momentum eigenstates are related by a Fourier transform. In order to calculate scattering probability, for example, one works in momentum space by choice since conservation of energy and momentum give considerable kinematic simplifications. But one does not have to do the calculation for every momentum in the superposition constituting the original wave packet: one chooses a typical momentum and works with that eigenstate alone. If one wants to recreate the packet effect, a simple integration over the momentum distribution is all that is required. So introducing a multiplicity of copies of Bob, each with its own measurement angle, is a red herring. One need consider only one typical orientation, because in the final analysis, there is only one polarizer setting for Bob that has to be compared with Alice's polarizer setting. The important point remains the same -- the settings for both Alice and Bob are chose and set classically by decoherence long before they ever meet up again. So the relative angle is not determined only when their future light cones overlap -- that relative angle was set when they were at a spacelike separation. it's only when you choose to look at the sector where the settings were the same or opposite settings were chosen that you get the reduction of the number of states. But that sector is defined by what happens on both sides, so there is no strange non-local effect here that is present in collapse theories. The reduction from four to two sta
Re: Non-locality and MWI
On 09-05-2016 03:40, Bruce Kellett wrote: On 9/05/2016 2:58 am, smitra wrote: On 08-05-2016 01:52, Bruce Kellett wrote: The set-up of the experiment belies the second part of your comment. The information about the angles was not in the initial state. Sure, the dynamics of the interaction between the particles and the polarizer is local, and the polarizer angle is also set locally, but the entangled state that interacts with the polarizer is itself not local -- it is spread out in space. It is because the original entangled state is spread out that the polarizers at each end react in tandem -- giving rise to the non-locality. Interactions in this are all local, the non-locality arises from the fact that the singlet state itself is not localized. Yes, but that's again a trivial non-local effect as the entangled spins were created locally in the past. In the MWI this only gives rise to non-local effects that are trivial common cause effects, unlike in single World interpretations. It is not a common cause effect. The singlet state is, but the polarizer setting of A and B are independently and freely chosen after the particles are widely separated. There is no common cause for this. Alternatively, you can let Alice and Bob do additional measurements of quantum systems and then set the polarizer settings according to what they find. In that case the information about the settings was not put in the initial state but it then arises out of the dynamics. However, you then get a superposition of all possibilities, Superposition of all which possibilities? I imagine that what you are saying is that if the setting is chosen according to the outcome of some other quantum event, then all possible outcomes of that event are realized in different branches of a superposition, or in different worlds. This does not actually help you. Remember that each of the worlds in which these different settings obtain also contains a copy of the same particle that is part of the entangled pair (Alice measured the other part). So in each branch of your new superposition, the same state is measured in some direction. Whichever branch Bob then finds himself in, he still has eventually to communicate with Alice. And all the Bob's in this picture have their own particular theta and |+> or |-> result. The multiplication of possibilities for Bob has not removed the problem of how this theta is determined for each copy. The essential non-locality remains. The relative angle theta is not determined for each copy separately, each branch of Alice contains all the branches of Bob where Bob chooses some angle and vice versa. The relative angle is only going to be determined later when Alice and Bob communicate, it's only then that Alice and Bob get localized into branches where the relative angle is determined. This additional superposition that you are invoking is actually irrelevant. It is quite common in physics to deal with such superpositions by considering just one typical member of the superposition and performing the calculation for that particular case. The general superposed case can be added back later if required, but it does not add anything new. The paradigm illustration of this is in particle physics. Because of the uncertainty principle, a particle is effectively never in an eigenstate of either position or momentum -- it is typically a wave packet, in which the spreads over various position and momentum eigenstates are related by a Fourier transform. In order to calculate scattering probability, for example, one works in momentum space by choice since conservation of energy and momentum give considerable kinematic simplifications. But one does not have to do the calculation for every momentum in the superposition constituting the original wave packet: one chooses a typical momentum and works with that eigenstate alone. If one wants to recreate the packet effect, a simple integration over the momentum distribution is all that is required. So introducing a multiplicity of copies of Bob, each with its own measurement angle, is a red herring. One need consider only one typical orientation, because in the final analysis, there is only one polarizer setting for Bob that has to be compared with Alice's polarizer setting. The important point remains the same -- the settings for both Alice and Bob are chose and set classically by decoherence long before they ever meet up again. So the relative angle is not determined only when their future light cones overlap -- that relative angle was set when they were at a spacelike separation. it's only when you choose to look at the sector where the settings were the same or opposite settings were chosen that you get the reduction of the number of states. But that sector is defined by what happens on both sides, so there is no strange non-local effect here that is present in collapse theories. The reduction from four to two states has never been the problem
Re: Non-locality and MWI (literature)
On 9/05/2016 1:39 am, Bruno Marchal wrote: Thanks Scerir. Very interesting. On 08 May 2016, at 09:58, 'scerir' via Everything List wrote: https://arxiv.org/abs/1501.03521 'Bell on Bell's theorem: The changing face of nonlocality' Authors: Harvey R. Brown, Christopher G. Timpson there are several interesting points here ch. 9 - Locality in the Everett picture ch. 9.1 EPR and Bell correlations in the Everettian setting Nice. I think that what we are trying to explain to Bruce is well summed up in their section 9.1.2 (the Everett description of the singlet state, case of non-align polarizer). I have already discussed this in my reply to Saibal. The basic point I would make again is that the splitting of the universal wave function into separate "worlds" is an interpretive gloss that does not actually alter anything in the theory. Furthermore, 'who knows what about whatever' is also an irrelevance as far as the universal wave function is concerned. If you are going to work in the many worlds paradigm, then everything ultimately stems from the unitary evolution of the universal wave function -- all else is just interpretive gloss, of no fundamental significance. This is the case for the discussion in section 9.1.2 of the paper by Brown and Timpson. Their equation (9) contains all the relevant results that set the universal wave function -- the additional third measurement (or measurement-like interaction) leading to equation (10) is, therefore, irrelevant. All that happens in eq. (10) is an exchange of information -- but it is an exchange of information that is already present in the universal wave function, no new information is created at this point. Just like opening the box on Schrödinger's cat, which is either alive or dead long before, looking changes nothing. Eq. (10) is, similarly, just an interpretive gloss of no fundamental significance. The important point here is that everything is set in the universal wave function /before/ Alice and Bob meet. The relative angle of the respective polarizers is set in the wave function long before the light cones of Alice and Bob overlap, so that relative angle is determined non-locally. The universal wave function is not a local object -- the unitary evolution does not have any implicit notion of locality. Locality is a human convention, and the universal wave function is under no compulsion to take any notice of human conventions or preferences. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 9/05/2016 2:58 am, smitra wrote: On 08-05-2016 01:52, Bruce Kellett wrote: The set-up of the experiment belies the second part of your comment. The information about the angles was not in the initial state. Sure, the dynamics of the interaction between the particles and the polarizer is local, and the polarizer angle is also set locally, but the entangled state that interacts with the polarizer is itself not local -- it is spread out in space. It is because the original entangled state is spread out that the polarizers at each end react in tandem -- giving rise to the non-locality. Interactions in this are all local, the non-locality arises from the fact that the singlet state itself is not localized. Yes, but that's again a trivial non-local effect as the entangled spins were created locally in the past. In the MWI this only gives rise to non-local effects that are trivial common cause effects, unlike in single World interpretations. It is not a common cause effect. The singlet state is, but the polarizer setting of A and B are independently and freely chosen after the particles are widely separated. There is no common cause for this. Alternatively, you can let Alice and Bob do additional measurements of quantum systems and then set the polarizer settings according to what they find. In that case the information about the settings was not put in the initial state but it then arises out of the dynamics. However, you then get a superposition of all possibilities, Superposition of all which possibilities? I imagine that what you are saying is that if the setting is chosen according to the outcome of some other quantum event, then all possible outcomes of that event are realized in different branches of a superposition, or in different worlds. This does not actually help you. Remember that each of the worlds in which these different settings obtain also contains a copy of the same particle that is part of the entangled pair (Alice measured the other part). So in each branch of your new superposition, the same state is measured in some direction. Whichever branch Bob then finds himself in, he still has eventually to communicate with Alice. And all the Bob's in this picture have their own particular theta and |+> or |-> result. The multiplication of possibilities for Bob has not removed the problem of how this theta is determined for each copy. The essential non-locality remains. The relative angle theta is not determined for each copy separately, each branch of Alice contains all the branches of Bob where Bob chooses some angle and vice versa. The relative angle is only going to be determined later when Alice and Bob communicate, it's only then that Alice and Bob get localized into branches where the relative angle is determined. This additional superposition that you are invoking is actually irrelevant. It is quite common in physics to deal with such superpositions by considering just one typical member of the superposition and performing the calculation for that particular case. The general superposed case can be added back later if required, but it does not add anything new. The paradigm illustration of this is in particle physics. Because of the uncertainty principle, a particle is effectively never in an eigenstate of either position or momentum -- it is typically a wave packet, in which the spreads over various position and momentum eigenstates are related by a Fourier transform. In order to calculate scattering probability, for example, one works in momentum space by choice since conservation of energy and momentum give considerable kinematic simplifications. But one does not have to do the calculation for every momentum in the superposition constituting the original wave packet: one chooses a typical momentum and works with that eigenstate alone. If one wants to recreate the packet effect, a simple integration over the momentum distribution is all that is required. So introducing a multiplicity of copies of Bob, each with its own measurement angle, is a red herring. One need consider only one typical orientation, because in the final analysis, there is only one polarizer setting for Bob that has to be compared with Alice's polarizer setting. The important point remains the same -- the settings for both Alice and Bob are chose and set classically by decoherence long before they ever meet up again. So the relative angle is not determined only when their future light cones overlap -- that relative angle was set when they were at a spacelike separation. it's only when you choose to look at the sector where the settings were the same or opposite settings were chosen that you get the reduction of the number of states. But that sector is defined by what happens on both sides, so there is no strange non-local effect here that is present in collapse theories. The reduction from four to two states has never been the problem -- it is the origin
Re: Non-locality and MWI
On 08-05-2016 01:52, Bruce Kellett wrote: On 8/05/2016 3:11 am, smitra wrote: On 07-05-2016 09:03, Bruce Kellett wrote: There is no such additional superposition in the quantum formalism, so if you are going to postulate one such, then you are talking about some different theory, not quantum mechanics. If you have a problem with the reduction of 4 outcomes to two outcomes, then you need to trace back where the information implied by this originated from. Your current argument is hiding this. In the theory where there is no collapse that has non-local features and where there are only local interactions, the information about the angles was either put a priori in the initial state (you can have modeled it in the effective Hamiltonian that describes how Alice's and Bob's spin will interact with the polarizers), or it arose out of the dynamics itself. In neither case does the result point to some strange non-local effect. I don't understand where you got this from. I do not have a problem with the reduction from 4 outcomes to 2 outcomes in the case of parallel polarizers -- it is there in the formalism: two of the terms vanish when theta=0º. You seem to be implying that there cannot be any non-local effects in QM because it is, by definition, a local theory. The apparent locality of the theory is why some people have so much trouble understanding the non-local effects that can arise in QM. I quote the following from a recent post on another list by an experienced physicist: "An entangled pair of states just share the same wave function, and the uncertainty principle is ultimately what is behind the nonlocality of the wave function. A wave function with a spread means there is no localization of the wave. This is even for a classical wave, which prior to the quantum physics was not seen as a problem. Yet when that wave was found to describe the motion of a material particle then suddenly all types of strange issues came forth. This extended in some ways to the quantum theory of light for entangled states of polarization and so forth. "The spread of a wave, which for a spherical wave front can be considerable, and the uncertainty principle are the primary reasons for all of these nonlocal physics." What is being said here is related to what I said recently about working in momentum space: in momentum space particles are completely non-localized. Non-locality is now widely accepted as a fact of quantum theory. It cannot be removed by definition! The set-up of the experiment belies the second part of your comment. The information about the angles was not in the initial state. Sure, the dynamics of the interaction between the particles and the polarizer is local, and the polarizer angle is also set locally, but the entangled state that interacts with the polarizer is itself not local -- it is spread out in space. It is because the original entangled state is spread out that the polarizers at each end react in tandem -- giving rise to the non-locality. Interactions in this are all local, the non-locality arises from the fact that the singlet state itself is not localized. Yes, but that's again a trivial non-local effect as the entangled spins were created locally in the past. In the MWI this only gives rise to non-local effects that are trivial common cause effects, unlike in single World interpretations. . You have clearly not understood the basic weirdness of quantum mechanics. I have, but it's clear that you refuse the analyze this problem properly according to the MWI. What you do is you take the l formalism of how we compute things in practice as "the truth" when it's not the truth according to the MWI. So what is the MWI "truth"? How is the standard quantum calculation modified? Remember, that the quantum formalism is taken to be the most complete possible formulation of the state -- if you go beyond this formulation, by calling on additional non-visible information, for instance, you are no longer talking about quantum mechanics but some other theory. There is no modification, MWI demands that all physical degrees of freedom are included in the Schrödinger equation, if you want to describe the physical situation in terms of macroscopic observers, you are necessarily going to have to resort to an effective treatment of the problem.In MWI language one introduces "branches" that describe the sectors where the observers find different outcomes. Here one makes hidden assumptions whose validity in theoretical arguments must always be checked. The reduction of 4 outcomes to 2 outcomes is not a non-local effect in the MWI, because the information contained in the absence of ++ and -- outcomes did not arise in a non-local way. If you have a real collapse then there is problem. But in the MWI all possible outcomes are realized, and if we are to assume that Alice and Bob's polarizer settings were predetermined then you have hidden this information in the init
Re: Non-locality and MWI (literature)
Thanks Scerir. Very interesting. On 08 May 2016, at 09:58, 'scerir' via Everything List wrote: https://arxiv.org/abs/1501.03521 'Bell on Bell's theorem: The changing face of nonlocality' Authors: Harvey R. Brown, Christopher G. Timpson there are several interesting points here ch. 9 - Locality in the Everett picture ch. 9.1 EPR and Bell correlations in the Everettian setting Nice. I think that what we are trying to explain to Bruce is well summed up in their section 9.1.2 (the Everett description of the singlet state, case of non-align polarizer). I think Saunders and Wallace also got that point, and that is equivalent with Tipler (plus some reasonable assumptions) The only real problem for Everett is that he uses a form of "comp" which now asks for a phenomenological account of the waves itself, and the symmetries and the apparent breaking of the symmetries. The nice surprise is that not only that approach seems to work, (thanks to the discovery of the universal machine (computer science) and of the Gödel-Löbian machine), but that approach makes possible to split the logics and theories obtained (for those phenomenologies, implied by incompleteness) and to distinguish truth and the justifiable, truth and the observable, truth and the knowable, truth and the sensible, etc. It is handy to get the relation right between the quanta and the qualia. We cannot derive the existence of a universal machine/system/language without assuming such a universal system. But once we believe in one of them, like when we believe in elementary arithmetic or in the Fortran programming language, we get all the others and the many internal phenomenologies, which are not dependent of the initial choice we make to tlak about them. Once you assume computationalism (under the weak form of Church thesis + consciousness invariance for a relatively- digital substitution) Peano Arithmetic (+ computationalism thus) can prove the existence of a web of dreams and of a limiting multiverse (locally stable and sharable first person plural points of view. Bruno etc. etc. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 8/05/2016 3:11 am, smitra wrote: On 07-05-2016 09:03, Bruce Kellett wrote: There is no such additional superposition in the quantum formalism, so if you are going to postulate one such, then you are talking about some different theory, not quantum mechanics. If you have a problem with the reduction of 4 outcomes to two outcomes, then you need to trace back where the information implied by this originated from. Your current argument is hiding this. In the theory where there is no collapse that has non-local features and where there are only local interactions, the information about the angles was either put a priori in the initial state (you can have modeled it in the effective Hamiltonian that describes how Alice's and Bob's spin will interact with the polarizers), or it arose out of the dynamics itself. In neither case does the result point to some strange non-local effect. I don't understand where you got this from. I do not have a problem with the reduction from 4 outcomes to 2 outcomes in the case of parallel polarizers -- it is there in the formalism: two of the terms vanish when theta=0º. You seem to be implying that there cannot be any non-local effects in QM because it is, by definition, a local theory. The apparent locality of the theory is why some people have so much trouble understanding the non-local effects that can arise in QM. I quote the following from a recent post on another list by an experienced physicist: "An entangled pair of states just share the same wave function, and the uncertainty principle is ultimately what is behind the nonlocality of the wave function. A wave function with a spread means there is no localization of the wave. This is even for a classical wave, which prior to the quantum physics was not seen as a problem. Yet when that wave was found to describe the motion of a material particle then suddenly all types of strange issues came forth. This extended in some ways to the quantum theory of light for entangled states of polarization and so forth. "The spread of a wave, which for a spherical wave front can be considerable, and the uncertainty principle are the primary reasons for all of these nonlocal physics." What is being said here is related to what I said recently about working in momentum space: in momentum space particles are completely non-localized. Non-locality is now widely accepted as a fact of quantum theory. It cannot be removed by definition! The set-up of the experiment belies the second part of your comment. The information about the angles was not in the initial state. Sure, the dynamics of the interaction between the particles and the polarizer is local, and the polarizer angle is also set locally, but the entangled state that interacts with the polarizer is itself not local -- it is spread out in space. It is because the original entangled state is spread out that the polarizers at each end react in tandem -- giving rise to the non-locality. Interactions in this are all local, the non-locality arises from the fact that the singlet state itself is not localized. . You have clearly not understood the basic weirdness of quantum mechanics. I have, but it's clear that you refuse the analyze this problem properly according to the MWI. What you do is you take the l formalism of how we compute things in practice as "the truth" when it's not the truth according to the MWI. So what is the MWI "truth"? How is the standard quantum calculation modified? Remember, that the quantum formalism is taken to be the most complete possible formulation of the state -- if you go beyond this formulation, by calling on additional non-visible information, for instance, you are no longer talking about quantum mechanics but some other theory. The reduction of 4 outcomes to 2 outcomes is not a non-local effect in the MWI, because the information contained in the absence of ++ and -- outcomes did not arise in a non-local way. If you have a real collapse then there is problem. But in the MWI all possible outcomes are realized, and if we are to assume that Alice and Bob's polarizer settings were predetermined then you have hidden this information in the initial state or the effective dynamics. There is no assumption that Alice and Bob's settings were predetermined -- that is explicitly ruled out in the formulation of the problem. Alternatively, you can let Alice and Bob do additional measurements of quantum systems and then set the polarizer settings according to what they find. In that case the information about the settings was not put in the initial state but it then arises out of the dynamics. However, you then get a superposition of all possibilities, Superposition of all which possibilities? I imagine that what you are saying is that if the setting is chosen according to the outcome of some other quantum event, then all possible outcomes of that event are realized in di
Re: Non-locality and MWI
On 07-05-2016 09:03, Bruce Kellett wrote: On 7/05/2016 4:28 pm, Brent Meeker wrote: On 5/6/2016 10:51 PM, smitra wrote: On 07-05-2016 02:36, Bruce Kellett wrote: The use of the relative orientation angle theta is intrinsically non-local. That angle cannot be obtained by local means in the above derivation. The equation for |psi> derived above shows the full coherent wave function as evolved from the initial state according Schrödinger's equation. There is nothing else -- no more worlds or dopplegangers than the four explicitly shown. The observers can only differentiate into one of these four worlds. And that is correct -- it is in agreement with experience. But it is still non-local. It is wrong to invoke this angle in this way in the MWI. While it leads to the correct answer, one has to consider that the evolution of the state vector is still due to local dynamics. It's therefore a trivial fact that there cannot be any non-local effects here. The illusion of a non-local effect comes from cutting corners in the derivation by assuming that there exists a macroscopic Alice here with some polarizer setting and a macroscopic Bob over there with some other polarizer setting and then we can can compute the correlations by just applying the usual formalism. And then we make hidden assumptions based on the classical behavior of Alice, Bob and the polarizers as they are macroscopic. That sounds reasonable, it also yields the correct answer but it's still wrong as a description of the physical situation according to the MWI. A correct MWI derivation must involve working with a wavefunction that evolves under unitary time evolution. But that wavefunction is a function of different points in space, some of which are spacelike separate. The wf dynamically evolves the probabilistic location of the singlet particles to their interaction with the polarizers and detectors. The interaction at the polarizers changes the wf at other locations. In the usual formalism this change is instantaneous, i.e. spacelike. If it's not instantaneous, as Rubin argued, then it must propagate within the forward lightcone and the reduced wf only describes the correlation in the part of spacetime in which the forward lightcones of Alice and Bob's measurments overlap. Yes, there is nothing in the derivation that violates unitary evolution. Some details are left out, certainly, but nothing of any importance. A wave is extended over space and intrinsically non-local. In momentum space, positions are completely undetermined, so calculations in momentum space are the epitome of non-locality. If you do that you're just going to re-derive the same old result, but using a much more cumbersome formalism. But that cumbersome formalism then does falsify your claim that the MWI is non-local. The crucial point where your analysis is faulty is when you invoke the angle in an ad hoc way. The angle arises from the setting of the polarizers, we can e.g. assume that the polarizers were set a priori to some settings and that information was known globally. But then there is no issue with non-locality. You can also assume that Alice and Bob decide to choose the polarizer settings later, but then the evolution of Alice and Bob leading up to their choices must be included in the dynamics. If we are to assume that Alice cannot even in principle know what Bob's setting is, then that means that the physically correct state will be a superposition of many different polarizer settings for both Alice and Bob. There is no such additional superposition in the quantum formalism, so if you are going to postulate one such, then you are talking about some different theory, not quantum mechanics. If you have a problem with the reduction of 4 outcomes to two outcomes, then you need to trace back where the information implied by this originated from. Your current argument is hiding this. In the theory where there is no collapse that has non-local features and where there are only local interactions, the information about the angles was either put a priori in the initial state (you can have modeled it in the effective Hamiltonian that describes how Alice's and Bob's spin will interact with the polarizers), or it arose out of the dynamics itself. In neither case does the result point to some strange non-local effect. That doesn't follow. Suppose the polarizers are set according to the detection or not of a photon from distant stars who are opposite on another on the celestial sphere. Alice can see how her polarizer is set and Bob can see his, so there's no need to postulate a superposition; but their seeing of the settings are spacelike. While you can project out the subspace where Alice chooses some angle and finds some particular result and then claim that if Bob had chose that same angle two of the four outcomes would mysteriously have vanished, there isn't anything on Bob's side that makes him make that same choice. Invoking that he'l
Re: Non-locality and MWI
On 07-05-2016 08:28, Brent Meeker wrote: On 5/6/2016 10:51 PM, smitra wrote: On 07-05-2016 02:36, Bruce Kellett wrote: The use of the relative orientation angle theta is intrinsically non-local. That angle cannot be obtained by local means in the above derivation. The equation for |psi> derived above shows the full coherent wave function as evolved from the initial state according Schrödinger's equation. There is nothing else -- no more worlds or dopplegangers than the four explicitly shown. The observers can only differentiate into one of these four worlds. And that is correct -- it is in agreement with experience. But it is still non-local. It is wrong to invoke this angle in this way in the MWI. While it leads to the correct answer, one has to consider that the evolution of the state vector is still due to local dynamics. It's therefore a trivial fact that there cannot be any non-local effects here. The illusion of a non-local effect comes from cutting corners in the derivation by assuming that there exists a macroscopic Alice here with some polarizer setting and a macroscopic Bob over there with some other polarizer setting and then we can can compute the correlations by just applying the usual formalism. And then we make hidden assumptions based on the classical behavior of Alice, Bob and the polarizers as they are macroscopic. That sounds reasonable, it also yields the correct answer but it's still wrong as a description of the physical situation according to the MWI. A correct MWI derivation must involve working with a wavefunction that evolves under unitary time evolution. But that wavefunction is a function of different points in space, some of which are spacelike separate. The wf dynamically evolves the probabilistic location of the singlet particles to their interaction with the polarizers and detectors. The interaction at the polarizers changes the wf at other locations. In the usual formalism this change is instantaneous, i.e. spacelike. If it's not instantaneous, as Rubin argued, then it must propagate within the forward lightcone and the reduced wf only describes the correlation in the part of spacetime in which the forward lightcones of Alice and Bob's measurments overlap. Yes, but this leads to only apparent non-local effects that are all due to trivial "common cause effects". If you do that you're just going to re-derive the same old result, but using a much more cumbersome formalism. But that cumbersome formalism then does falsify your claim that the MWI is non-local. The crucial point where your analysis is faulty is when you invoke the angle in an ad hoc way. The angle arises from the setting of the polarizers, we can e.g. assume that the polarizers were set a priori to some settings and that information was known globally. But then there is no issue with non-locality. You can also assume that Alice and Bob decide to choose the polarizer settings later, but then the evolution of Alice and Bob leading up to their choices must be included in the dynamics. If we are to assume that Alice cannot even in principle know what Bob's setting is, then that means that the physically correct state will be a superposition of many different polarizer settings for both Alice and Bob. That doesn't follow. Suppose the polarizers are set according to the detection or not of a photon from distant stars who are opposite on another on the celestial sphere. Alice can see how her polarizer is set and Bob can see his, so there's no need to postulate a superposition; but their seeing of the settings are spacelike. That doesn't matter, my point is that you need to account for the entire system. If you invoke photons emitted by some distant star, you need to include these details in your description and then see if you still get some strange non-local effect, where "strange" means that it isn't the sort of trivial common cause effect. While you can project out the subspace where Alice chooses some angle and finds some particular result and then claim that if Bob had chose that same angle two of the four outcomes would mysteriously have vanished, there isn't anything on Bob's side that makes him make that same choice. Invoking that he'll do so amounts to just planting the information that exists on Alice side to Bob's side, that's then not a non-local effect at all. But when the results are compared Alice and Bob will be able to sort out which results went with which polarizer settings. That's how the correlation is seen. No one claims that this can used to communicate FTL. Only that the interactions are spacelike and violate Bell's inequality. Yes, but it's only in single World theories that there is a problem here. In the case bith have chosen the same settings, Alice knows that there were 2 possible outcomes for her and Bob also has two possible outcomes. They know that there are no local hidden variables, therefore what e
Re: Non-locality and MWI
On 7/05/2016 4:28 pm, Brent Meeker wrote: On 5/6/2016 10:51 PM, smitra wrote: On 07-05-2016 02:36, Bruce Kellett wrote: The use of the relative orientation angle theta is intrinsically non-local. That angle cannot be obtained by local means in the above derivation. The equation for |psi> derived above shows the full coherent wave function as evolved from the initial state according Schrödinger's equation. There is nothing else -- no more worlds or dopplegangers than the four explicitly shown. The observers can only differentiate into one of these four worlds. And that is correct -- it is in agreement with experience. But it is still non-local. It is wrong to invoke this angle in this way in the MWI. While it leads to the correct answer, one has to consider that the evolution of the state vector is still due to local dynamics. It's therefore a trivial fact that there cannot be any non-local effects here. The illusion of a non-local effect comes from cutting corners in the derivation by assuming that there exists a macroscopic Alice here with some polarizer setting and a macroscopic Bob over there with some other polarizer setting and then we can can compute the correlations by just applying the usual formalism. And then we make hidden assumptions based on the classical behavior of Alice, Bob and the polarizers as they are macroscopic. That sounds reasonable, it also yields the correct answer but it's still wrong as a description of the physical situation according to the MWI. A correct MWI derivation must involve working with a wavefunction that evolves under unitary time evolution. But that wavefunction is a function of different points in space, some of which are spacelike separate. The wf dynamically evolves the probabilistic location of the singlet particles to their interaction with the polarizers and detectors. The interaction at the polarizers changes the wf at other locations. In the usual formalism this change is instantaneous, i.e. spacelike. If it's not instantaneous, as Rubin argued, then it must propagate within the forward lightcone and the reduced wf only describes the correlation in the part of spacetime in which the forward lightcones of Alice and Bob's measurments overlap. Yes, there is nothing in the derivation that violates unitary evolution. Some details are left out, certainly, but nothing of any importance. A wave is extended over space and intrinsically non-local. In momentum space, positions are completely undetermined, so calculations in momentum space are the epitome of non-locality. If you do that you're just going to re-derive the same old result, but using a much more cumbersome formalism. But that cumbersome formalism then does falsify your claim that the MWI is non-local. The crucial point where your analysis is faulty is when you invoke the angle in an ad hoc way. The angle arises from the setting of the polarizers, we can e.g. assume that the polarizers were set a priori to some settings and that information was known globally. But then there is no issue with non-locality. You can also assume that Alice and Bob decide to choose the polarizer settings later, but then the evolution of Alice and Bob leading up to their choices must be included in the dynamics. If we are to assume that Alice cannot even in principle know what Bob's setting is, then that means that the physically correct state will be a superposition of many different polarizer settings for both Alice and Bob. There is no such additional superposition in the quantum formalism, so if you are going to postulate one such, then you are talking about some different theory, not quantum mechanics. That doesn't follow. Suppose the polarizers are set according to the detection or not of a photon from distant stars who are opposite on another on the celestial sphere. Alice can see how her polarizer is set and Bob can see his, so there's no need to postulate a superposition; but their seeing of the settings are spacelike. While you can project out the subspace where Alice chooses some angle and finds some particular result and then claim that if Bob had chose that same angle two of the four outcomes would mysteriously have vanished, there isn't anything on Bob's side that makes him make that same choice. Invoking that he'll do so amounts to just planting the information that exists on Alice side to Bob's side, that's then not a non-local effect at all. But when the results are compared Alice and Bob will be able to sort out which results went with which polarizer settings. That's how the correlation is seen. No one claims that this can used to communicate FTL. Only that the interactions are spacelike and violate Bell's inequality. Not only with which polarizer setting, but also from which particular entangled pair. Alice has to have some way of knowing that a particular result (and polarizer setting) came from the same entangled
Re: Non-locality and MWI
On 5/6/2016 10:51 PM, smitra wrote: On 07-05-2016 02:36, Bruce Kellett wrote: The use of the relative orientation angle theta is intrinsically non-local. That angle cannot be obtained by local means in the above derivation. The equation for |psi> derived above shows the full coherent wave function as evolved from the initial state according Schrödinger's equation. There is nothing else -- no more worlds or dopplegangers than the four explicitly shown. The observers can only differentiate into one of these four worlds. And that is correct -- it is in agreement with experience. But it is still non-local. It is wrong to invoke this angle in this way in the MWI. While it leads to the correct answer, one has to consider that the evolution of the state vector is still due to local dynamics. It's therefore a trivial fact that there cannot be any non-local effects here. The illusion of a non-local effect comes from cutting corners in the derivation by assuming that there exists a macroscopic Alice here with some polarizer setting and a macroscopic Bob over there with some other polarizer setting and then we can can compute the correlations by just applying the usual formalism. And then we make hidden assumptions based on the classical behavior of Alice, Bob and the polarizers as they are macroscopic. That sounds reasonable, it also yields the correct answer but it's still wrong as a description of the physical situation according to the MWI. A correct MWI derivation must involve working with a wavefunction that evolves under unitary time evolution. But that wavefunction is a function of different points in space, some of which are spacelike separate. The wf dynamically evolves the probabilistic location of the singlet particles to their interaction with the polarizers and detectors. The interaction at the polarizers changes the wf at other locations. In the usual formalism this change is instantaneous, i.e. spacelike. If it's not instantaneous, as Rubin argued, then it must propagate within the forward lightcone and the reduced wf only describes the correlation in the part of spacetime in which the forward lightcones of Alice and Bob's measurments overlap. If you do that you're just going to re-derive the same old result, but using a much more cumbersome formalism. But that cumbersome formalism then does falsify your claim that the MWI is non-local. The crucial point where your analysis is faulty is when you invoke the angle in an ad hoc way. The angle arises from the setting of the polarizers, we can e.g. assume that the polarizers were set a priori to some settings and that information was known globally. But then there is no issue with non-locality. You can also assume that Alice and Bob decide to choose the polarizer settings later, but then the evolution of Alice and Bob leading up to their choices must be included in the dynamics. If we are to assume that Alice cannot even in principle know what Bob's setting is, then that means that the physically correct state will be a superposition of many different polarizer settings for both Alice and Bob. That doesn't follow. Suppose the polarizers are set according to the detection or not of a photon from distant stars who are opposite on another on the celestial sphere. Alice can see how her polarizer is set and Bob can see his, so there's no need to postulate a superposition; but their seeing of the settings are spacelike. While you can project out the subspace where Alice chooses some angle and finds some particular result and then claim that if Bob had chose that same angle two of the four outcomes would mysteriously have vanished, there isn't anything on Bob's side that makes him make that same choice. Invoking that he'll do so amounts to just planting the information that exists on Alice side to Bob's side, that's then not a non-local effect at all. But when the results are compared Alice and Bob will be able to sort out which results went with which polarizer settings. That's how the correlation is seen. No one claims that this can used to communicate FTL. Only that the interactions are spacelike and violate Bell's inequality. Brent If we are to assume that Bob's and Alice's settings were fixed, so we eliminate this improper planting of information from Alice's side to Bob's side, then you have to ask how it's possible that Bob's polarizer setting would always come out the same way as Alice's? Clearly you've then build this in in the dynamics so, you've hidden a non-local correlation in the Hamiltonian that describes the time evolution. The bottom line is that a manifestly local theory cannot possibly yield a non-local results other than via trivial common cause effects. Fundamentally there is nothing more to this thought experiment that handing Alice and Bob correlated playing cards. It's just that quantum mechanics gives you a bit more room to hide the tr
Re: Non-locality and MWI
On 07-05-2016 02:36, Bruce Kellett wrote: The use of the relative orientation angle theta is intrinsically non-local. That angle cannot be obtained by local means in the above derivation. The equation for |psi> derived above shows the full coherent wave function as evolved from the initial state according Schrödinger's equation. There is nothing else -- no more worlds or dopplegangers than the four explicitly shown. The observers can only differentiate into one of these four worlds. And that is correct -- it is in agreement with experience. But it is still non-local. It is wrong to invoke this angle in this way in the MWI. While it leads to the correct answer, one has to consider that the evolution of the state vector is still due to local dynamics. It's therefore a trivial fact that there cannot be any non-local effects here. The illusion of a non-local effect comes from cutting corners in the derivation by assuming that there exists a macroscopic Alice here with some polarizer setting and a macroscopic Bob over there with some other polarizer setting and then we can can compute the correlations by just applying the usual formalism. And then we make hidden assumptions based on the classical behavior of Alice, Bob and the polarizers as they are macroscopic. That sounds reasonable, it also yields the correct answer but it's still wrong as a description of the physical situation according to the MWI. A correct MWI derivation must involve working with a wavefunction that evolves under unitary time evolution. If you do that you're just going to re-derive the same old result, but using a much more cumbersome formalism. But that cumbersome formalism then does falsify your claim that the MWI is non-local. The crucial point where your analysis is faulty is when you invoke the angle in an ad hoc way. The angle arises from the setting of the polarizers, we can e.g. assume that the polarizers were set a priori to some settings and that information was known globally. But then there is no issue with non-locality. You can also assume that Alice and Bob decide to choose the polarizer settings later, but then the evolution of Alice and Bob leading up to their choices must be included in the dynamics. If we are to assume that Alice cannot even in principle know what Bob's setting is, then that means that the physically correct state will be a superposition of many different polarizer settings for both Alice and Bob. While you can project out the subspace where Alice chooses some angle and finds some particular result and then claim that if Bob had chose that same angle two of the four outcomes would mysteriously have vanished, there isn't anything on Bob's side that makes him make that same choice. Invoking that he'll do so amounts to just planting the information that exists on Alice side to Bob's side, that's then not a non-local effect at all. If we are to assume that Bob's and Alice's settings were fixed, so we eliminate this improper planting of information from Alice's side to Bob's side, then you have to ask how it's possible that Bob's polarizer setting would always come out the same way as Alice's? Clearly you've then build this in in the dynamics so, you've hidden a non-local correlation in the Hamiltonian that describes the time evolution. The bottom line is that a manifestly local theory cannot possibly yield a non-local results other than via trivial common cause effects. Fundamentally there is nothing more to this thought experiment that handing Alice and Bob correlated playing cards. It's just that quantum mechanics gives you a bit more room to hide the trick. Saibal -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 7/05/2016 2:50 am, Bruno Marchal wrote: On 06 May 2016, at 01:13, Bruce Kellett wrote: There is a widely cited paper by Tipler (arxiv:quant-ph/0003146v1) that claims to show the MWI does away with non-locality. I read it a long time ago, but I have stopped to believe that MWI can be non-local before. If you agree that a world is a sect of object/event close for interaction, then Jesse mazer argument directly leads to locality. Jesse's model may be local, but it does not reproduce the observed correlations. Where Alice is separated from Bob light cone, she can be in the same world at all. There will be no action at a distance because there will no interaction possible. This is your basic linguistic confusion at work again. It is because the interaction occurs between spacelike separated objects (where no local interaction is possible) that it is said to be non-local. The correlation will not be confirmed by them, but only by their respective doppelganger which will inhabit their worlds soon or later. You have yet to make this particular mantra work in the sense of a physical model. And by a physical model I mean an account that starts with a well-defined initial state and follows its time evolution in terms of well-defined dynamical laws (generally expressed in the form of differential equations). It is instructive to go through his argument, and to see how he has managed to deceive himself. We start with the singlet state: |psi> = (|+>|-> - |->|+>)/sqrt(2) and then expand the state for the second particle in a different basis (at relative angle theta): |+>_2 = cos(theta/2)*|+'> + sin(theta/2)*|-'>, |->_2 = -sin(theta/2)*|+'> + cos(theta/2)*|-'>. Substituting this into the singlet state above, we get |psi> = -[ sin(theta/2)*|+>|+'> - cos(theta/2)*|+>|-'> + cos(theta/2)*|->|+'> + sin(theta/2)*|->+'>]/sqrt(2), which exactly represents the requisite four worlds, corresponding to the (+,+'), (+,-'), (-,+'), and (-,-') possibilities for joint results, each world weighted by the required probability. OK, but you cannot look at them like if it was a mixture. No collapse has ever occurred, nor will ever occur. I have expressly said that I am working in the MWI paradigm -- I make no appeal to collapse of any kind. Tipler claims that this shows how the standard statistics come about by local measurements splitting the universe into distinct worlds. He is, of course, deluding himself, because the above calculation is not local. That does not make sense to me. The calculation is local. What it depicts is a coherent whole which behave thorugh local interactions, with the apparition of phenomenological indeterminacy and non locality due to the fact that the observers differentiates. The use of the relative orientation angle theta is intrinsically non-local. That angle cannot be obtained by local means in the above derivation. The equation for |psi> derived above shows the full coherent wave function as evolved from the initial state according Schrödinger's equation. There is nothing else -- no more worlds or dopplegangers than the four explicitly shown. The observers can only differentiate into one of these four worlds. And that is correct -- it is in agreement with experience. But it is still non-local. It is, in fact, nothing more that the standard quantum calculations (with the projection postulate evident) Yes, but the projection is only a first person (plural intra world) view. But the above equation does not involve projection! Projection only comes from the individuals self-locating in one of the four possible worlds. that I gave above for the possible (+) and (-) results for Alice, combined in the one equation. It still uses the fact that Alice's measurement of particle 1 affects the quantum state for particle 2 (which is, by then, a large spacelike distance away). I don't see that. You need to do a bit more work. Tipler utilizes the non-local nature of this change to extract theta, the relative orientation of magnets -- a relative orientation that can only be known by comparing orientations at A and B directly. So Tipler's derivation is every bit as much local or non-local as the conventional calculation -- he has not eliminated non-locality by his trivial reworking of the derivation. But non-locality never entered in the picture. It is only the abstraction of the parallel states which make us feel something has acted at the distance, but what the many Alice and Bob are doing is just localizing themselves in the universes (first person plural view) that they can share. That makes no sense in terms of the physics. Tipler's calculation is exemplary in every way as a standard quantum calculation on this entangled state. He has merely ignored the effects of decoherence in order to retain the full superposition. Decoherence is only superposition contagion. It is done as sublight speed, and
Re: Non-locality and MWI
On 7/05/2016 2:50 am, Bruno Marchal wrote: On 06 May 2016, at 01:13, Bruce Kellett wrote: But this does not work, as Feynman and Everett already explained with the double slit. In "Fabric of Reality" David Deutsch made it even clearer using for slits. You are confusing the Feynman paths of the path integral formalism with separate worlds. I did not. David Deutsch is famous for this particular idiotic confusion. You have just defined a 'world' above as a set of things closed for interaction. On that definition (with which I agree), the paths through the separate slits in a two-slit set-up cannot be separate worlds -- they are just separate paths in the Feynman sense. All they need to be are different terms in the wave expansion. They are superposed states/worlds/situations/whatever. That just leads to linguistic confusion. And the more linguistically confused you become, the less able you are to reason clearly. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: R: Re: Non-locality and MWI
>Interesting, but my schedule makes it hard for me to analyse this just >now. Now, if you think you can argue for non-locality from Renninger >type of measurement, don't hesitate to show us. Here the point was >just that the violation of Bell's inequality does not lead to non- >local action, unless measurement leads to single realities. > >A long time ago, I convinced my self that Elizur Vaidman type of >measurement without interaction might be problematic with the MWI, but >that was not the case. Is Renninger measurement related to this? Well Vaidman wrote something about that. "The word “measurement” in quantum theory have many very different meanings. The purpose of the Renninger and Dicke measurements is preparation of a quantum state. In contrast, the purpose of the EV [Elitzur-Vaidman] interaction-free measurement is to obtain information about the object. In Renninger and Dicke measurements the measuring device is undisturbed (these are negative result experiments) while in the EV measurement the observed object is, in some sense, undisturbed. In fact, in general EV IFM the quantum state of the observed object is disturbed: the wave function becomes localized at the vicinity of the lower arm of the interferometer (see Sec. 3 of the EV paper). The reasons for using the term “interaction-free measurements” are that the object does not explode (if it is a bomb), it does not absorb any photon (if it is an opaque object) and that we can claim that, in some sense, the photon does not reach the vicinity of the object." "I can see something in common between the Renninger–Dicke IFM and the EV IFM in the framework of the many-worlds interpretation. In both cases there is an ‘‘interaction’’: radiation of the scintillator in the Renninger experiment or explosion of the bomb in the EV experiment, but these interactions take place in the ‘‘other’’ branch, not in the branch we end up discussing the experiment. In an attempt to avoid adopting the many-worlds interpretation such interactions were considered as counterfactual." "Reasoning in the framework of the many-worlds interpretation (MWI ) leads to the statement that while we can find an object in the interaction-free manner, we cannot find out that a certain place is empty in the interaction-free way. Here, I mean ‘‘interaction-free’’ in the sense that no photons (or other particles) pass through the place in question. Getting information about some location in space without any particle being there is paradoxical because physical laws include only local interactions. In the case of finding the bomb, the MWI solves the paradox. Indeed, the laws apply to the whole physical Universe which includes all the worlds and, therefore, the reasoning must be true only when we consider all the worlds. Since there are worlds with the explosion we cannot say on the level of the physical Universe that no photons were at the location of the bomb. In contrast, when there is no bomb, there are no other worlds. The paradox in our world becomes the paradox for the whole Universe which is a real paradox. Thus, it is impossible to find a procedure which tests the presence of an object in a particular place such that no particles visit the place both in the case the object is there and in the case the object is not there. Quantitative analysis of the limitations due to this effect were recently performed by Reif who called the task ‘‘interaction-free sensing.’’. This effect also leads to limitations on the efficiency of ‘‘interaction-free computation’’ when all possible outcomes are considered." See, in example, this paper http://www.tau.ac.il/~vaidman/lvhp/m87.pdf > >Of course, with computationalism all this are open problem. Would the >physics extracted from computationalism leads to non-locality, I would >decide to be a gardiner ;) > >Bruno Well being a farmer, not a mathematician, I can make a mistake. So when Vaidman writes "Getting information about some location in space without any particle being there is paradoxical because physical laws include only local interactions" actually he is talking about *some* sort of non-locality. At least, this is my humble feeling. s. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 06 May 2016, at 01:13, Bruce Kellett wrote: On 5/05/2016 10:57 pm, Bruno Marchal wrote: On 05 May 2016, at 01:31, Bruce Kellett wrote: This is where your fascination with the 1p-3p notion gets you into trouble. If the third person view (3p) means anything at all, it means simple intersubjective agreement. The third person is one who stands outside the particular experimental situation and observes the outcome. In the 'Quantum Darwinism' of Zeh, this corresponds to the fact that decoherence leaves many traces of a particular experimental result in the environment; this result can be shared among many 'third persons' without degradation -- hence intersubjective agreement. There is no 'person' who has the 'bird' view -- there is no-one who continues to see the superposition after dechorence has had its way. Your 1p-3p distinction works for person-copying, as in taking copies of a computer program, because there can be a third person who sees both copies, the one in Washington and the one in Moscow. Nothing similar is possible in the quantum case, so your continued use of the 'peepee' language in discussions of quantum mechanics isjust confused. I will at the positive aspect. You seem to agree with the computationalist FPI. That is a progress. Now just reread Everett. Pure state evolves in pure state, and never becomes mixture in the MW. The third person view is given by the wave or matric formalism. The relative state are given by partial trace. We can define a world by a set of things close for interaction, this automatically ensure locality. MWI with the partial trace, required in order that experiments give definite results, does give the transition froma pure state to a mixture. Certainly, the only sensible definition of a wolrd is a set of things closed for interaction -- this requires the partial trace, by the way, To claim that this automatically ensures locality is just nonsense. ... As I said, there is no 'person' who has the 'bird' view. It is just your belief that this is the fundamental ontology. You have absolutely no direct evidence for this, nor could you have. The fundamental ontology could just be one world, with the universal wave function as nothing more than a calculational device -- you could not know the difference. But this does not work, as Feynman and Everett already explained with the double slit. In "Fabric of Reality" David Deutsch made it even clearer using for slits. You are confusing the Feynman paths of the path integral formalism with separate worlds. I did not. David Deutsch is famous for this particular idiotic confusion. You have just defined a 'world' above as a set of things closed for interaction. On that definition (with which I agree), the paths through the separate slits in a two-slit set-up cannot be separate worlds -- they are just separate paths in the Feynman sense. All they need to be are different terms in the wave expansion. They are superposed states/worlds/situations/whatever. .. As I expected, you simply duck the problem and make a fatuous appeal to authority. I have shown explicitly that the argument given by Tipler fails. You have to rebut my argument. I did. The error is in factoring Alice (+) state, which is impossible as her memory has changed in the two branches. Rubbish. You seem to forget the argument that Tipler actually made. I reproduce it here: here I was referring to the debunking of your idea that Alice cannot get right the result of repeated measurement. You come back on a different thread. There is a widely cited paper by Tipler (arxiv:quant-ph/0003146v1) that claims to show the MWI does away with non-locality. I read it a long time ago, but I have stopped to believe that MWI can be non-local before. If you agree that a world is a sect of object/ event close for interaction, then Jesse mazer argument directly leads to locality. Where Alice is separated from Bob light cone, she can be in the same world at all. There will be no action at a distance because there will no interaction possible. The correlation will not be confirmed by them, but only by their respective doppelganger which will inhabit their worlds soon or later. It is instructive to go through his argument, and to see how he has managed to deceive himself. We start with the singlet state: |psi> = (|+>|-> - |->|+>)/sqrt(2) and then expand the state for the second particle in a different basis (at relative angle theta): |+>_2 = cos(theta/2)*|+'> + sin(theta/2)*|-'>, |->_2 = -sin(theta/2)*|+'> + cos(theta/2)*|-'>. Substituting this into the singlet state above, we get |psi> = -[ sin(theta/2)*|+>|+'> - cos(theta/2)*|+>|-'> + cos(theta/2)*|->|+'> + sin(theta/2)*|->+'>]/sqrt(2), which exactly represents the requisite four worlds, corresponding to the (+,+'), (+,-'), (-,
Re: Non-locality and MWI
On 05 May 2016, at 22:40, Brent Meeker wrote: On 5/5/2016 5:57 AM, Bruno Marchal wrote: I will at the positive aspect. You seem to agree with the computationalist FPI. That is a progress. Now just reread Everett. Pure state evolves in pure state, and never becomes mixture in the MW. The third person view is given by the wave or matric formalism. The relative state are given by partial trace. We can define a world by a set of things close for interaction, this automatically ensure locality. But the partial trace is not a physical process, it's choice of the analyst. Although decoherence provides some guidance it doesn't completely solve the Heisenberg cut problem. And even after taking the partial trace and getting a reduced, diagonal density matrix there is no physical principle for saying which are realized and why the trace in that basis instead of another. I think that the FPI is enough. The partial trace is not physical, but its phenomenology is real and dictated by the choice of the measuring apparatus. It would be physically real, like with the collapse, then we would have action at a distance. Roland Omnes looks at this analysis and says, "QM is a probabilistic theory. So when it predicts probabilities that all you can expect." One of its book is the most brilliant defense of the MWI, but in the last paragraph of the book, he admit hating that idea, and decide that it was time to be irrational and decide that some God selects one physical reality. Bruno Brent -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI
On 05 May 2016, at 19:43, 'scerir' via Everything List wrote: Bruno writes: Alice * (up + down) = Alice * up + Alice * down. If Alice look, as many times as she want at the up/down state of the particle, she will find up (and always up) *and* down and always down. The reason is that once she find up, Alice becomes Alice-up, and that state does no more factor out the particle state (unless memory erasure). --- The paradox of the "Renninger type measurement" is that it causes some changes in the state of the system “WITHOUT INTERACTION.” Renninger discussed a “NEGATIVE RESULT” experiment: a situation in which the detector DOES NOT DETECT ANYTHING. But in spite of the fact that nothing happened to the detector, there is a change in the measured system (split, collapse, reduction, or whatever). He considered a spherical wave of a photon after it extended beyond the radius at which a scintillation detector was located in part of the solid angle. The state of the detector remained unchanged but, nevertheless, the wave- function of the photon is modified. See ch. 4.1 here http://mist.npl.washington.edu/npl/int_rep/tiqm/TI_40.html and also http://mist.npl.washington.edu/npl/int_rep/tiqm/TI_fig_06.html How is it possible to explain this situation? In MWI terms? In ManyMinds terms? Third person pov? First person pov? I'm asking that because there is a strange mixture of (physical) reality and (subjective) information here. Interesting, but my schedule makes it hard for me to analyse this just now. Now, if you think you can argue for non-locality from Renninger type of measurement, don't hesitate to show us. Here the point was just that the violation of Bell's inequality does not lead to non- local action, unless measurement leads to single realities. A long time ago, I convinced my self that Elizur Vaidman type of measurement without interaction might be problematic with the MWI, but that was not the case. Is Renninger measurement related to this? Of course, with computationalism all this are open problem. Would the physics extracted from computationalism leads to non-locality, I would decide to be a gardiner ;) Bruno -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 5/05/2016 10:57 pm, Bruno Marchal wrote: On 05 May 2016, at 01:31, Bruce Kellett wrote: This is where your fascination with the 1p-3p notion gets you into trouble. If the third person view (3p) means anything at all, it means simple intersubjective agreement. The third person is one who stands outside the particular experimental situation and observes the outcome. In the 'Quantum Darwinism' of Zeh, this corresponds to the fact that decoherence leaves many traces of a particular experimental result in the environment; this result can be shared among many 'third persons' without degradation -- hence intersubjective agreement. There is no 'person' who has the 'bird' view -- there is no-one who continues to see the superposition after dechorence has had its way. Your 1p-3p distinction works for person-copying, as in taking copies of a computer program, because there can be a third person who sees both copies, the one in Washington and the one in Moscow. Nothing similar is possible in the quantum case, so your continued use of the 'peepee' language in discussions of quantum mechanics is just confused. I will at the positive aspect. You seem to agree with the computationalist FPI. That is a progress. Now just reread Everett. Pure state evolves in pure state, and never becomes mixture in the MW. The third person view is given by the wave or matric formalism. The relative state are given by partial trace. We can define a world by a set of things close for interaction, this automatically ensure locality. MWI with the partial trace, required in order that experiments give definite results, does give the transition froma pure state to a mixture. Certainly, the only sensible definition of a wolrd is a set of things closed for interaction -- this requires the partial trace, by the way, To claim that this automatically ensures locality is just nonsense. ... As I said, there is no 'person' who has the 'bird' view. It is just your belief that this is the fundamental ontology. You have absolutely no direct evidence for this, nor could you have. The fundamental ontology could just be one world, with the universal wave function as nothing more than a calculational device -- you could not know the difference. But this does not work, as Feynman and Everett already explained with the double slit. In "Fabric of Reality" David Deutsch made it even clearer using for slits. You are confusing the Feynman paths of the path integral formalism with separate worlds. David Deutsch is famous for this particular idiotic confusion. You have just defined a 'world' above as a set of things closed for interaction. On that definition (with which I agree), the paths through the separate slits in a two-slit set-up cannot be separate worlds -- they are just separate paths in the Feynman sense. .. As I expected, you simply duck the problem and make a fatuous appeal to authority. I have shown explicitly that the argument given by Tipler fails. You have to rebut my argument. I did. The error is in factoring Alice (+) state, which is impossible as her memory has changed in the two branches. Rubbish. You seem to forget the argument that Tipler actually made. I reproduce it here: There is a widely cited paper by Tipler (arxiv:quant-ph/0003146v1) that claims to show the MWI does away with non-locality. It is instructive to go through his argument, and to see how he has managed to deceive himself. We start with the singlet state: |psi> = (|+>|-> - |->|+>)/sqrt(2) and then expand the state for the second particle in a different basis (at relative angle theta): |+>_2 = cos(theta/2)*|+'> + sin(theta/2)*|-'>, |->_2 = -sin(theta/2)*|+'> + cos(theta/2)*|-'>. Substituting this into the singlet state above, we get |psi> = -[ sin(theta/2)*|+>|+'> - cos(theta/2)*|+>|-'> + cos(theta/2)*|->|+'> + sin(theta/2)*|->+'>]/sqrt(2), which exactly represents the requisite four worlds, corresponding to the (+,+'), (+,-'), (-,+'), and (-,-') possibilities for joint results, each world weighted by the required probability. Tipler claims that this shows how the standard statistics come about by local measurements splitting the universe into distinct worlds. He is, of course, deluding himself, because the above calculation is not local. It is, in fact, nothing more that the standard quantum calculations (with the projection postulate evident) that I gave above for the possible (+) and (-) results for Alice, combined in the one equation. It still uses the fact that Alice's measurement of particle 1 affects the quantum state for particle 2 (which is, by then, a large spacelike distance away). Tipler utilizes the non-local nature of this change to extract theta, the relative orientation of magnets -- a relative orientation that can only be known by comparing orientations at A and B directly. So Tipler's derivation is every bit as much local or non-local as
Re: Non-locality and MWI
On 5/5/2016 5:57 AM, Bruno Marchal wrote: I will at the positive aspect. You seem to agree with the computationalist FPI. That is a progress. Now just reread Everett. Pure state evolves in pure state, and never becomes mixture in the MW. The third person view is given by the wave or matric formalism. The relative state are given by partial trace. We can define a world by a set of things close for interaction, this automatically ensure locality. But the partial trace is not a physical process, it's choice of the analyst. Although decoherence provides some guidance it doesn't completely solve the Heisenberg cut problem. And even after taking the partial trace and getting a reduced, diagonal density matrix there is no physical principle for saying which are realized and why the trace in that basis instead of another. Roland Omnes looks at this analysis and says, "QM is a probabilistic theory. So when it predicts probabilities that all you can expect." Brent -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: Non-locality and MWI
Bruno writes: Alice * (up + down) = Alice * up + Alice * down. If Alice look, as many times as she want at the up/down state of the particle, she will find up (and always up) *and* down and always down. The reason is that once she find up, Alice becomes Alice-up, and that state does no more factor out the particle state (unless memory erasure). --- The paradox of the "Renninger type measurement" is that it causes some changes in the state of the system “WITHOUT INTERACTION.” Renninger discussed a “NEGATIVE RESULT” experiment: a situation in which the detector DOES NOT DETECT ANYTHING. But in spite of the fact that nothing happened to the detector, there is a change in the measured system (split, collapse, reduction, or whatever). He considered a spherical wave of a photon after it extended beyond the radius at which a scintillation detector was located in part of the solid angle. The state of the detector remained unchanged but, nevertheless, the wave- function of the photon is modified. See ch. 4.1 here http://mist.npl.washington.edu/npl/int_rep/tiqm/TI_40.html and also http://mist.npl.washington.edu/npl/int_rep/tiqm/TI_fig_06.html How is it possible to explain this situation? In MWI terms? In ManyMinds terms? Third person pov? First person pov? I'm asking that because there is a strange mixture of (physical) reality and (subjective) information here. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 05 May 2016, at 01:31, Bruce Kellett wrote: On 5/05/2016 5:17 am, Bruno Marchal wrote: On 04 May 2016, at 01:25, Bruce Kellett wrote: On 4/05/2016 3:41 am, Bruno Marchal wrote: On 03 May 2016, at 00:32, Bruce Kellett wrote: On 3/05/2016 1:49 am, Bruno Marchal wrote: On 02 May 2016, at 07:54, Bruce Kellett wrote: On 2/05/2016 3:15 pm, Jesse Mazer wrote: On Mon, May 2, 2016 at 12:13 AM, Bruce Kellett > wrote: No, I disagree. The setting b has no effect on what happens at a remote location is sufficiently precise to encapsulate exactly what physicists mean by locality. In quantum field theory, this is generalized to the notion of local causality, which is the statement that the commutators of all spacelike separate variables vanish -- as you mention below. And if you used full quantum description of the measuring apparatus and experimenter, and didn't assume any collapse on measurement, then there would in general be no single "setting b" in the region of spacetime where one experimenter was choosing a setting, but rather a superposition of different settings. Do you think your preferred definition can be meaningfully applied to this case, and if so how? I do not know what you here mean by "collapse on measurement"? It seems that you might be confusing a collapse to a single world after measurement with the projection postulate of standard quantum theory. The projection postulate is essential if one is to get stable physical results -- repeated openings of the box in Schrödinger's cat experiments would result in oscillations between dead and alive cats. The projection postulate is replaced by the FPI in Everett, and as I explained yesterday, it is just self-entanglement, or what I call often the contagion of superposition: Alice * (up + down) = Alice * up + Alice * down. If Alice look, as many times as she want at the up/down state of the particle, she will find up (and always up) *and* down and always down. The reason is that once she find up, Alice becomes Alice-up, and that state does no more factor out the particle state (unless memory erasure). That is just the projection postulate, it cannot be replaced if you want to agree with observation. Well OK. If that is the projection postulate, then it is a theorem in QM-without collapse, through the direct use of the First Person Indeterminacy. As I thought, you have confused this with the collapse of the wave function to a single world. That is the confusion of the Copenhagen people, who believe (correctly) that a measurement select one world among many, but believe (incorrectly) that the other worlds, or wave suterms, have mysteriously disappear. With Everett analysis of measurement, we have: Alice * (up + down) = Alice * up + Alice * down. (linearity of tensor product), and it becomes: Alice-seeing-up * up + Alice-seeing-down * down (linearity of time evolution) With the copenhagen collapse of the wave, we have: Alice * (up + down) = Alice * up + Alice * down. (linearity of tensor product), and it becomes Alice-seeing-up * up (non-linearity of time evolution) or Alice-seeing-down * down (again with a non-linearity of time evolution) The proportion of worlds, or the probability of results being given by the (square-root of 1/2)^2 (= 1/2), square root hidden above for reason of readability. When it is boiled down, this is nothing more than a matter of taste. By concentrating on the individual worlds, so that A(|+>|-> - |->|+>) --> A(+)|+>|-> OR A(-)|->|+> where A(+) means "Alice sees + as her result", and so on, the conventional understanding simply implements the insights coming from decoherence and wider entanglement with the environment, leading to the emergence of disjointworlds: the original pure state reduces to a mixed state (represented by the use of 'OR' in the above equation) as a result of the partial trace over environmental degrees of freedom. The alternative formulation (where 'OR' is replaced by '+') simply retains the original pure state and does not represent the formation of disjoint worlds following environmental decoherence. ? You talk like if the conventional understanding as many-worlds, and the MW was not leading to Many worlds. I find it difficult to parse this sentence. The conventional understanding is that decoherence and the partial trace reduces the original pure state to a mixture. This is necessary if one wants the theory to produce definite results from experiments, rather than superpositions. The resulting 'worlds', if you want to call them that, are disjoint and do not have any influence on one another. If you want to believe that all the 'worlds' exist, then feel free, but that belief has no operational consequences -- Occam's Razor is the usual way of dispensing with such redundancies. This is sometimes referred to (following T
Re: Non-locality and MWI
On 5/05/2016 5:17 am, Bruno Marchal wrote: On 04 May 2016, at 01:25, Bruce Kellett wrote: On 4/05/2016 3:41 am, Bruno Marchal wrote: On 03 May 2016, at 00:32, Bruce Kellett wrote: On 3/05/2016 1:49 am, Bruno Marchal wrote: On 02 May 2016, at 07:54, Bruce Kellett wrote: On 2/05/2016 3:15 pm, Jesse Mazer wrote: On Mon, May 2, 2016 at 12:13 AM, Bruce Kellett wrote: No, I disagree. The setting *b* has no effect on what happens at a remote location is sufficiently precise to encapsulate exactly what physicists mean by locality. In quantum field theory, this is generalized to the notion of local causality, which is the statement that the commutators of all spacelike separate variables vanish -- as you mention below. And if you used full quantum description of the measuring apparatus and experimenter, and didn't assume any collapse on measurement, then there would in general be no single "setting b" in the region of spacetime where one experimenter was choosing a setting, but rather a superposition of different settings. Do you think your preferred definition can be meaningfully applied to this case, and if so how? I do not know what you here mean by "collapse on measurement"? It seems that you might be confusing a collapse to a single world after measurement with the projection postulate of standard quantum theory. The projection postulate is essential if one is to get stable physical results -- repeated openings of the box in Schrödinger's cat experiments would result in oscillations between dead and alive cats. The projection postulate is replaced by the FPI in Everett, and as I explained yesterday, it is just self-entanglement, or what I call often the contagion of superposition: Alice * (up + down) = Alice * up + Alice * down. If Alice look, as many times as she want at the up/down state of the particle, she will find up (and always up) *and* down and always down. The reason is that once she find up, Alice becomes Alice-up, and that state does no more factor out the particle state (unless memory erasure). That is just the projection postulate, it cannot be replaced if you want to agree with observation. Well OK. If that is the projection postulate, then it is a theorem in QM-without collapse, through the direct use of the First Person Indeterminacy. As I thought, you have confused this with the collapse of the wave function to a single world. That is the confusion of the Copenhagen people, who believe (correctly) that a measurement select one world among many, but believe (incorrectly) that the other worlds, or wave suterms, have mysteriously disappear. With Everett analysis of measurement, we have: Alice * (up + down) = Alice * up + Alice * down. (linearity of tensor product), and it becomes: Alice-seeing-up * up + Alice-seeing-down * down (linearity of time evolution) With the copenhagen collapse of the wave, we have: Alice * (up + down) = Alice * up + Alice * down. (linearity of tensor product), and it becomes Alice-seeing-up * up (non-linearity of time evolution) or Alice-seeing-down * down (again with a non-linearity of time evolution) The proportion of worlds, or the probability of results being given by the (square-root of 1/2)^2 (= 1/2), square root hidden above for reason of readability. When it is boiled down, this is nothing more than a matter of taste. By concentrating on the individual worlds, so that A(|+>|-> - |->|+>) --> A(+)|+>|-> OR A(-)|->|+> where A(+) means "Alice sees + as her result", and so on, the conventional understanding simply implements the insights coming from decoherence and wider entanglement with the environment, leading to the emergence of disjoint worlds: the original pure state reduces to a mixed state (represented by the use of 'OR' in the above equation) as a result of the partial trace over environmental degrees of freedom. The alternative formulation (where 'OR' is replaced by '+') simply retains the original pure state and does not represent the formation of disjoint worlds following environmental decoherence. ? You talk like if the conventional understanding as many-worlds, and the MW was not leading to Many worlds. I find it difficult to parse this sentence. The conventional understanding is that decoherence and the partial trace reduces the original pure state to a mixture. This is necessary if one wants the theory to produce definite results from experiments, rather than superpositions. The resulting 'worlds', if you want to call them that, are disjoint and do not have any influence on one another. If you want to believe that all the 'worlds' exist, then feel free, but that belief has no operational consequences -- Occam's Razor is the usual way of dispensing with such redundancies. This is sometimes referred to (following Tegmark) as the difference between the 'frog' and 'bird' views. (It is more precisly the di
Re: Non-locality and MWI
On 04 May 2016, at 01:25, Bruce Kellett wrote: On 4/05/2016 3:41 am, Bruno Marchal wrote: On 03 May 2016, at 00:32, Bruce Kellett wrote: On 3/05/2016 1:49 am, Bruno Marchal wrote: On 02 May 2016, at 07:54, Bruce Kellett wrote: On 2/05/2016 3:15 pm, Jesse Mazer wrote: On Mon, May 2, 2016 at 12:13 AM, Bruce Kellett > wrote: No, I disagree. The setting b has no effect on what happens at a remote location is sufficiently precise to encapsulate exactly what physicists mean by locality. In quantum field theory, this is generalized to the notion of local causality, which is the statement that the commutators of all spacelike separate variables vanish -- as you mention below. And if you used full quantum description of the measuring apparatus and experimenter, and didn't assume any collapse on measurement, then there would in general be no single "setting b" in the region of spacetime where one experimenter was choosing a setting, but rather a superposition of different settings. Do you think your preferred definition can be meaningfully applied to this case, and if so how? I do not know what you here mean by "collapse on measurement"? It seems that you might be confusing a collapse to a single world after measurement with the projection postulate of standard quantum theory. The projection postulate is essential if one is to get stable physical results -- repeated openings of the box in Schrödinger's cat experiments would result in oscillations between dead and alive cats. The projection postulate is replaced by the FPI in Everett, and as I explained yesterday, it is just self-entanglement, or what I call often the contagion of superposition: Alice * (up + down) = Alice * up + Alice * down. If Alice look, as many times as she want at the up/down state of the particle, she will find up (and always up) *and* down and always down. The reason is that once she find up, Alice becomes Alice-up, and that state does no more factor out the particle state (unless memory erasure). That is just the projection postulate, it cannot be replaced if you want to agree with observation. Well OK. If that is the projection postulate, then it is a theorem in QM-without collapse, through the direct use of the First Person Indeterminacy. As I thought, you have confused this with the collapse of the wave function to a single world. That is the confusion of the Copenhagen people, who believe (correctly) that a measurement select one world among many, but believe (incorrectly) that the other worlds, or wave suterms, have mysteriously disappear. With Everett analysis of measurement, we have: Alice * (up + down) = Alice * up + Alice * down. (linearity of tensor product), and it becomes: Alice-seeing-up * up + Alice-seeing-down * down (linearity of time evolution) With the copenhagen collapse of the wave, we have: Alice * (up + down) = Alice * up + Alice * down. (linearity of tensor product), and it becomes Alice-seeing-up * up (non-linearity of time evolution) or Alice-seeing-down * down (again with a non-linearity of time evolution) The proportion of worlds, or the probability of results being given by the (square-root of 1/2)^2 (= 1/2), square root hidden above for reason of readability. When it is boiled down, this is nothing more than a matter of taste. By concentrating on the individual worlds, so that A(|+>|-> - |->|+>) --> A(+)|+>|-> OR A(-)|->|+> where A(+) means "Alice sees + as her result", and so on, the conventional understanding simply implements the insights coming from decoherence and wider entanglement with the environment, leading to the emergence of disjoint worlds: the original pure state reduces to a mixed state (represented by the use of 'OR' in the above equation) as a result of the partial trace over environmental degrees of freedom. The alternative formulation (where 'OR' is replaced by '+') simply retains the original pure state and does not represent the formation of disjoint worlds following environmental decoherence. ? You talk like if the conventional understanding as many-worlds, and the MW was not leading to Many worlds. This is sometimes referred to (following Tegmark) as the difference between the 'frog' and 'bird' views. (It is more precisly the difference between the first person view and the third person view. It is not a question of scaling. Nothing substantial hangs on this -- it is just a difference of perspective which adds nothing to the state. The 'frog' view is what you would call a result of FPI: OK. Nice you see that. I see it as a result of the formation of actual disjoint worlds that continue to evolve separately, never to influence one another again. The 'bird' view is an abstraction that never actually influences anyone or anything. The bird view is the universal wave, or the universal deployment
Re: Non-locality and MWI
On 4/05/2016 3:41 am, Bruno Marchal wrote: On 03 May 2016, at 00:32, Bruce Kellett wrote: On 3/05/2016 1:49 am, Bruno Marchal wrote: On 02 May 2016, at 07:54, Bruce Kellett wrote: On 2/05/2016 3:15 pm, Jesse Mazer wrote: On Mon, May 2, 2016 at 12:13 AM, Bruce Kellett mailto:bhkell...@optusnet.com.au>> wrote: No, I disagree. The setting *b* has no effect on what happens at a remote location is sufficiently precise to encapsulate exactly what physicists mean by locality. In quantum field theory, this is generalized to the notion of local causality, which is the statement that the commutators of all spacelike separate variables vanish -- as you mention below. And if you used full quantum description of the measuring apparatus and experimenter, and didn't assume any collapse on measurement, then there would in general be no single "setting b" in the region of spacetime where one experimenter was choosing a setting, but rather a superposition of different settings. Do you think your preferred definition can be meaningfully applied to this case, and if so how? I do not know what you here mean by "collapse on measurement"? It seems that you might be confusing a collapse to a single world after measurement with the projection postulate of standard quantum theory. The projection postulate is essential if one is to get stable physical results -- repeated openings of the box in Schrödinger's cat experiments would result in oscillations between dead and alive cats. The projection postulate is replaced by the FPI in Everett, and as I explained yesterday, it is just self-entanglement, or what I call often the contagion of superposition: Alice * (up + down) = Alice * up + Alice * down. If Alice look, as many times as she want at the up/down state of the particle, she will find up (and always up) *and* down and always down. The reason is that once she find up, Alice becomes Alice-up, and that state does no more factor out the particle state (unless memory erasure). That is just the projection postulate, it cannot be replaced if you want to agree with observation. Well OK. If that is the projection postulate, then it is a theorem in QM-without collapse, through the direct use of the First Person Indeterminacy. As I thought, you have confused this with the collapse of the wave function to a single world. That is the confusion of the Copenhagen people, who believe (correctly) that a measurement select one world among many, but believe (incorrectly) that the other worlds, or wave suterms, have mysteriously disappear. With Everett analysis of measurement, we have: Alice * (up + down) = Alice * up + Alice * down. (linearity of tensor product), and it becomes: Alice-seeing-up * up + Alice-seeing-down * down (linearity of time evolution) With the copenhagen collapse of the wave, we have: Alice * (up + down) = Alice * up + Alice * down. (linearity of tensor product), and it becomes Alice-seeing-up * up (non-linearity of time evolution) or Alice-seeing-down * down (again with a non-linearity of time evolution) The proportion of worlds, or the probability of results being given by the (square-root of 1/2)^2 (= 1/2), square root hidden above for reason of readability. When it is boiled down, this is nothing more than a matter of taste. By concentrating on the individual worlds, so that A(|+>|-> - |->|+>) --> A(+)|+>|-> OR A(-)|->|+> where A(+) means "Alice sees + as her result", and so on, the conventional understanding simply implements the insights coming from decoherence and wider entanglement with the environment, leading to the emergence of disjoint worlds: the original pure state reduces to a mixed state (represented by the use of 'OR' in the above equation) as a result of the partial trace over environmental degrees of freedom. The alternative formulation (where 'OR' is replaced by '+') simply retains the original pure state and does not represent the formation of disjoint worlds following environmental decoherence. This is sometimes referred to (following Tegmark) as the difference between the 'frog' and 'bird' views. Nothing substantial hangs on this -- it is just a difference of perspective which adds nothing to the state. The 'frog' view is what you would call a result of FPI: I see it as a result of the formation of actual disjoint worlds that continue to evolve separately, never to influence one another again. The 'bird' view is an abstraction that never actually influences anyone or anything. Unless you sort out this confusion you will never understand quantum mechanics. You see a confusion, because sometimes I talk about the projection postulate in the copenhagen frame, where it is associated with the collapse during the corresponding measurement, and sometimes I talk about the projection postulate in the frame of the non-collapse formulation of QM (Everett), in which case there is n
Re: Non-locality and MWI
On 03 May 2016, at 00:32, Bruce Kellett wrote: On 3/05/2016 1:49 am, Bruno Marchal wrote: On 02 May 2016, at 07:54, Bruce Kellett wrote: On 2/05/2016 3:15 pm, Jesse Mazer wrote: On Mon, May 2, 2016 at 12:13 AM, Bruce Kellett > wrote: No, I disagree. The setting b has no effect on what happens at a remote location is sufficiently precise to encapsulate exactly what physicists mean by locality. In quantum field theory, this is generalized to the notion of local causality, which is the statement that the commutators of all spacelike separate variables vanish -- as you mention below. And if you used full quantum description of the measuring apparatus and experimenter, and didn't assume any collapse on measurement, then there would in general be no single "setting b" in the region of spacetime where one experimenter was choosing a setting, but rather a superposition of different settings. Do you think your preferred definition can be meaningfully applied to this case, and if so how? I do not know what you here mean by "collapse on measurement"? It seems that you might be confusing a collapse to a single world after measurement with the projection postulate of standard quantum theory. The projection postulate is essential if one is to get stable physical results -- repeated openings of the box in Schrödinger's cat experiments would result in oscillations between dead and alive cats. The projection postulate is replaced by the FPI in Everett, and as I explained yesterday, it is just self-entanglement, or what I call often the contagion of superposition: Alice * (up + down) = Alice * up + Alice * down. If Alice look, as many times as she want at the up/down state of the particle, she will find up (and always up) *and* down and always down. The reason is that once she find up, Alice becomes Alice-up, and that state does no more factor out the particle state (unless memory erasure). That is just the projection postulate, it cannot be replaced if you want to agree with observation. Well OK. If that is the projection postulate, then it is a theorem in QM-without collapse, through the direct use of the First Person Indeterminacy. As I thought, you have confused this with the collapse of the wave function to a single world. That is the confusion of the Copenhagen people, who believe (correctly) that a measurement select one world among many, but believe (incorrectly) that the other worlds, or wave suterms, have mysteriously disappear. With Everett analysis of measurement, we have: Alice * (up + down) = Alice * up + Alice * down. (linearity of tensor product), and it becomes: Alice-seeing-up * up + Alice-seeing-down * down (linearity of time evolution) With the copenhagen collapse of the wave, we have: Alice * (up + down) = Alice * up + Alice * down. (linearity of tensor product), and it becomes Alice-seeing-up * up (non-linearity of time evolution) or Alice-seeing-down * down (again with a non-linearity of time evolution) The proportion of worlds, or the probability of results being given by the (square-root of 1/2)^2 (= 1/2), square root hidden above for reason of readability. Unless you sort out this confusion you will never understand quantum mechanics. You see a confusion, because sometimes I talk about the projection postulate in the copenhagen frame, where it is associated with the collapse during the corresponding measurement, and sometimes I talk about the projection postulate in the frame of the non-collapse formulation of QM (Everett), in which case there is no collapse associated of course, but the differentiating or bifurcating realities/ computations (relative terms of the linear wave). See Price for the analysis of the singlet state in those terms. Or Tipler, that you interpreted incorrectly apparently by avoiding the first person indeterminacy. [Computationalist Aparte And with Digital Mechanism, the mind-body problem is reduced with the problem of justifying the wave-matrix itself from an apparently larger one: all halting computations (equivalently, all true sigma_1 arithmetical sentences). For this we can define "bet on p = 1" by []p & p, with p sigma_, with two slight but important variants ([]p & <>p, []p & <>p & p). The three of them gives rise to a quantization obeying quantum logic, with semantics in term of differentiating neighborhood, or (at the G* level) a more complicated limiting proximity structure. The key advantage is that such logics appears at the G* level (in case you have read one of my papers) and this help to understand the (giant) difference between the qualia and the quanta, by the difference between G and G* (inherited by the variants above, except []p & p, a very interesting fact actually, but I will stop here on this for now).] Hmm..., It looks like on this list, it is the same people who see spooky
Re: Non-locality and MWI
On 3/05/2016 1:49 am, Bruno Marchal wrote: On 02 May 2016, at 07:54, Bruce Kellett wrote: On 2/05/2016 3:15 pm, Jesse Mazer wrote: On Mon, May 2, 2016 at 12:13 AM, Bruce Kellett mailto:bhkell...@optusnet.com.au>> wrote: No, I disagree. The setting *b* has no effect on what happens at a remote location is sufficiently precise to encapsulate exactly what physicists mean by locality. In quantum field theory, this is generalized to the notion of local causality, which is the statement that the commutators of all spacelike separate variables vanish -- as you mention below. And if you used full quantum description of the measuring apparatus and experimenter, and didn't assume any collapse on measurement, then there would in general be no single "setting b" in the region of spacetime where one experimenter was choosing a setting, but rather a superposition of different settings. Do you think your preferred definition can be meaningfully applied to this case, and if so how? I do not know what you here mean by "collapse on measurement"? It seems that you might be confusing a collapse to a single world after measurement with the projection postulate of standard quantum theory. The projection postulate is essential if one is to get stable physical results -- repeated openings of the box in Schrödinger's cat experiments would result in oscillations between dead and alive cats. The projection postulate is replaced by the FPI in Everett, and as I explained yesterday, it is just self-entanglement, or what I call often the contagion of superposition: Alice * (up + down) = Alice * up + Alice * down. If Alice look, as many times as she want at the up/down state of the particle, she will find up (and always up) *and* down and always down. The reason is that once she find up, Alice becomes Alice-up, and that state does no more factor out the particle state (unless memory erasure). That is just the projection postulate, it cannot be replaced if you want to agree with observation. As I thought, you have confused this with the collapse of the wave function to a single world. Unless you sort out this confusion you will never understand quantum mechanics. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 02 May 2016, at 06:13, Bruce Kellett wrote: On 2/05/2016 1:31 pm, Jesse Mazer wrote: On Sun, May 1, 2016 at 8:49 PM, Bruce Kellett > wrote: On 2/05/2016 7:52 am, Jesse Mazer wrote: On Fri, Apr 29, 2016 at 8:32 PM, Bruce Kellett > wrote: That is a semantic matter. There is a problem if one insists that "non-local" means the propagation of a real physical influence (particle of wave) faster-than-light. But "non-locality" in standard quantum usage means the above -- the entangled state acts as a single physical unit even when its components are widely separated. I agree it's a semantic matter, but your description of the "standard quantum usage" doesn't seem to be accurate. Among physicists, the standard understanding of "local" and "non-local" in the context of Bell's theorem and relativity is the one I cited earlier--a theory is "local" if and only if the function that gives you the value of local variables at any given point P in spacetime (or gives the best possible probabilistic prediction about their values, in the case of a non-deterministic theory) only requires as input the values of local variables at other points that lie within P's past light cone, whereas a "non-local" theory would be one where the function requires knowledge of variables at a spacelike separation from P to generate the best possible prediction. As I mentioned, I think this is explained most clearly inBell's paper "La nouvelle cuisine" which you can find in the collection "Speakable and Unspeakable in Quantum Mechanics", and you can also find it discussed in other sources, http://arxiv.org/abs/0707.0401 for example. As for "acts as a single physical unit", that seems like a decidedly non-mathematical definition which physicists would steer clear of, unless you can provide a mathematical formalization or what you mean, or cite a mainstream source that provides one. I don't see any paper of the title you mention in my copy of "Speakable and Unspeakable in Quantum Mechanics", could you give a page number reference? It's on p. 232 of the 2nd edition, chapter 24. I only have access to the first edition -- this must refer to a later paper of Bell's. It is not in my book "speakable and unspeakable", but it is in my book " John S. Bell on The Foundations of Quantum Mechanics". edited by M. Bell, K. Gottfried, & M. Veltman, page 216 (published by World Scientific 2001, published originally in 1990). It seems to me that his argument that QM cannot be embedded in a local close theory relies on the assumption of definite unique outcomes for the measurement, instead of the Everett FPI. But I just glanced to it, and I will reread it. Bruno What I did find was chapter 8, "Locality in quantum mechanics: reply to critics" (pp. 63-66). In that chapter, Bell says: "...now we add the hypothesis of locality, that the setting b of a particular instrument has no effect on what happens, A, in a remote region, and likewise that a has no effect on B. With these local forms, it is not possible to find functions A and B and a probability distribution rho which give the correlations = - a.b." This is an informal statement of exactly the notion of locality or non-locality that I have been using all along. Your more convoluted statement may bear some relation to Bell's theory of local beables (chapter 7 of his book), but the complications are unnecessary -- the informal definition is the one most physicists would use in practice. I disagree, physicists generally only use informal definitions if it's obvious they could be formalized, or if they are *implied* by some more precise technical definition (the looser definition you mention above would be implied by the more precise one I mentioned, *if* one assumes there is a unique truth about the setting at b and the measurement A). No, I disagree. The setting b has no effect on what happens at a remote location is sufficiently precise to encapsulate exactly what physicists mean by locality. In quantum field theory, this is generalized to the notion of local causality, which is the statement that the commutators of all spacelike separate variables vanish -- as you mention below. If quantum mechanics is complete, then the current quantum state contains all the information about the system that is either available or relevant. Sure, if you include hidden variables, then you are saying that QM as currently formulated is incomplete. That may be the case, but even so, the given definition of locality still holds -- it is about FTL propagation of information, nothing else. My qualitative definition of non-locality is not non-standard -- it is the definition frequently used by Bell, and (almost) everyone else. Your definition seems to want to take account of some sort of hidden variables, such that the quantum state as
Re: Non-locality and MWI
On 02 May 2016, at 07:54, Bruce Kellett wrote: On 2/05/2016 3:15 pm, Jesse Mazer wrote: On Mon, May 2, 2016 at 12:13 AM, Bruce Kellett > wrote: No, I disagree. The setting b has no effect on what happens at a remote location is sufficiently precise to encapsulate exactly what physicists mean by locality. In quantum field theory, this is generalized to the notion of local causality, which is the statement that the commutators of all spacelike separate variables vanish -- as you mention below. And if you used full quantum description of the measuring apparatus and experimenter, and didn't assume any collapse on measurement, then there would in general be no single "setting b" in the region of spacetime where one experimenter was choosing a setting, but rather a superposition of different settings. Do you think your preferred definition can be meaningfully applied to this case, and if so how? I do not know what you here mean by "collapse on measurement"? It seems that you might be confusing a collapse to a single world after measurement with the projection postulate of standard quantum theory. The projection postulate is essential if one is to get stable physical results -- repeated openings of the box in Schrödinger's cat experiments would result in oscillations between dead and alive cats. The projection postulate is replaced by the FPI in Everett, and as I explained yesterday, it is just self-entanglement, or what I call often the contagion of superposition: Alice * (up + down) = Alice * up + Alice * down. If Alice look, as many times as she want at the up/down state of the particle, she will find up (and always up) *and* down and always down. The reason is that once she find up, Alice becomes Alice-up, and that state does no more factor out the particle state (unless memory erasure). Bruno This is ruled out by decoherence -- extended entanglement with the environment is irreversible, so the result after a completed measurement is that the system is in the eigenstate corresponding to the observed eigenvalue. This says nothing about whether or not the other eigenvalues are observed in the disjoint worlds of the MWI. It seems, if fact, that whether there is a particular setting of b in the remote region or not is not really an issue. Bob is measuring the same entangled pair as Alice, and he only ever has one setting: Alice may not know this setting until later, but this could scarcely be called a superposition of different settings -- this is not part of the standard quantum formalism, even in MWI. To Alice, before she exchanges notes with Bob, she merely knows that the quantum state of Bob's particle can be expressed in any number of possible bases, but that does not mean that there is a superposition over all of these alternative bases. Try writing such a superposition our in standard form if you need to convince yourself of this fact. My qualitative definition of non-locality is not non-standard -- it is the definition frequently used by Bell, and (almost) everyone else. Your definition seems to want to take account of some sort of hidden variables, such that the quantum state as written does not contain all the information about that state. There are no hidden variables in the MWI (though the definition of locality should be general enough to cover theories with hidden variables as well as ones with no hidden variables, since Bell's theorem is meant to rule out local realist theories of either type). The "quantum state as written" does not give any definite outcomes of measurements, only a set of amplitudes on different eigenvectors associated with particular eigenvalues, which are understood as possible measurement results. True, but not relevant for these purposes. I am not ruling out an Everettian interpretation of the state vector -- my definition of locality simply rules out faster than light (FTL) transfer of information. Given the standard quantum treatment of the entangled singlet state, non-locality is unavoidable. Without any assumption of "collapse", the *amplitudes* assigned to local measurements on either member of an entangled pair could be determined solely from amplitudes on locally-measurable variables in the past light cone--do you disagree? No, I don't disagree. But I also don't see the point -- the preparation of the singlet state is all that can be known about the states that either Alice or Bob have available for measurement. Addition information from the past light cone need be considered only if you want to pursue a "superdeterministic" theory in which A and B are not actually free to determine their measurement angles. That does not mean that there is actually a physical transfer of particles or waves FTL, it simply means that the state is a unity, and changing one part changes the whole st
Re: Non-locality and MWI
On 2/05/2016 3:31 pm, Jesse Mazer wrote: On Mon, May 2, 2016 at 1:10 AM, Bruce Kellett mailto:bhkell...@optusnet.com.au>> wrote: On 2/05/2016 1:31 pm, Jesse Mazer wrote: On Sun, May 1, 2016 at 8:49 PM, Bruce Kellett mailto:bhkell...@optusnet.com.au>> wrote: On 2/05/2016 7:52 am, Jesse Mazer wrote: On Fri, Apr 29, 2016 at 8:32 PM, Bruce Kellett mailto:bhkell...@optusnet.com.au>> wrote: That is a semantic matter. There is a problem if one insists that "non-local" means the propagation of a real physical influence (particle of wave) faster-than-light. But "non-locality" in standard quantum usage means the above -- the entangled state acts as a single physical unit even when its components are widely separated. I agree it's a semantic matter, but your description of the "standard quantum usage" doesn't seem to be accurate. Among physicists, the standard understanding of "local" and "non-local" in the context of Bell's theorem and relativity is the one I cited earlier--a theory is "local" if and only if the function that gives you the value of local variables at any given point P in spacetime (or gives the best possible probabilistic prediction about their values, in the case of a non-deterministic theory) only requires as input the values of local variables at other points that lie within P's past light cone, whereas a "non-local" theory would be one where the function requires knowledge of variables at a spacelike separation from P to generate the best possible prediction. As I mentioned, I think this is explained most clearly in Bell's paper "La nouvelle cuisine" which you can find in the collection "Speakable and Unspeakable in Quantum Mechanics", and you can also find it discussed in other sources, http://arxiv.org/abs/0707.0401 for example. As for "acts as a single physical unit", that seems like a decidedly non-mathematical definition which physicists would steer clear of, unless you can provide a mathematical formalization or what you mean, or cite a mainstream source that provides one. I don't see any paper of the title you mention in my copy of "Speakable and Unspeakable in Quantum Mechanics", could you give a page number reference? It's on p. 232 of the 2nd edition, chapter 24. I have now looked at the paper by Norsen. It seems that the more detailed definiton of locality does little more than remove the notion of "superdeterminism" from the equation -- the idea that things in the common past of A and B could conspire to give rise to the correlations. The paper by Norsen at http://arxiv.org/pdf/0707.0401v3.pdf does mention the issue of ruling out superdeterminism, but that wasn't what I was referring to when I talked about the definition in La nouvelle cuisine which is repeated in Norsen's paper. Rather I was talking about equation 1 on page 4 whose physical meaning in terms of past light cones is show in Fig. 2 on the same page. Referring to the diagram and equation, b1 refers to the physical state of local variables in region 1, b2 refers to the physical state of local variables in another region 2 at a spacelike separation of 1, and B3 refers to some sufficiently detailed set of local states in region 3 which is in the past light cone of region 1, but entirely outside the past light cone of region 2. The idea is that by picking a sufficiently detailed set for your B3, you can have it so that once you know B3, additional knowledge of b2 is irrelevant to your prediction of what's going on in b1, i.e. you don't need anything outside the past light cone of 1 to make the best possible physical prediction about the physical facts in that region. So, nothing to do with superdeterminism, just a more formal statement of the idea I described earlier about the function for making predictions about a given region depending only on facts in the past light cone of that region. And that is all I have ever claimed about locality -- that is what is built into the formal quantum description of the state. The more elaborate definition does not add anything substantive - it merely rules out some alternative formulations of the state that go beyond standard QM. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 2/05/2016 3:15 pm, Jesse Mazer wrote: On Mon, May 2, 2016 at 12:13 AM, Bruce Kellett mailto:bhkell...@optusnet.com.au>> wrote: No, I disagree. The setting *b* has no effect on what happens at a remote location is sufficiently precise to encapsulate exactly what physicists mean by locality. In quantum field theory, this is generalized to the notion of local causality, which is the statement that the commutators of all spacelike separate variables vanish -- as you mention below. And if you used full quantum description of the measuring apparatus and experimenter, and didn't assume any collapse on measurement, then there would in general be no single "setting b" in the region of spacetime where one experimenter was choosing a setting, but rather a superposition of different settings. Do you think your preferred definition can be meaningfully applied to this case, and if so how? I do not know what you here mean by "collapse on measurement"? It seems that you might be confusing a collapse to a single world after measurement with the projection postulate of standard quantum theory. The projection postulate is essential if one is to get stable physical results -- repeated openings of the box in Schrödinger's cat experiments would result in oscillations between dead and alive cats. This is ruled out by decoherence -- extended entanglement with the environment is irreversible, so the result after a completed measurement is that the system is in the eigenstate corresponding to the observed eigenvalue. This says nothing about whether or not the other eigenvalues are observed in the disjoint worlds of the MWI. It seems, if fact, that whether there is a particular setting of b in the remote region or not is not really an issue. Bob is measuring the same entangled pair as Alice, and he only ever has one setting: Alice may not know this setting until later, but this could scarcely be called a superposition of different settings -- this is not part of the standard quantum formalism, even in MWI. To Alice, before she exchanges notes with Bob, she merely knows that the quantum state of Bob's particle can be expressed in any number of possible bases, but that does not mean that there is a superposition over all of these alternative bases. Try writing such a superposition our in standard form if you need to convince yourself of this fact. My qualitative definition of non-locality is not non-standard -- it is the definition frequently used by Bell, and (almost) everyone else. Your definition seems to want to take account of some sort of hidden variables, such that the quantum state as written does not contain all the information about that state. There are no hidden variables in the MWI (though the definition of locality should be general enough to cover theories with hidden variables as well as ones with no hidden variables, since Bell's theorem is meant to rule out local realist theories of either type). The "quantum state as written" does not give any definite outcomes of measurements, only a set of amplitudes on different eigenvectors associated with particular eigenvalues, which are understood as possible measurement results. True, but not relevant for these purposes. I am not ruling out an Everettian interpretation of the state vector -- my definition of locality simply rules out faster than light (FTL) transfer of information. Given the standard quantum treatment of the entangled singlet state, non-locality is unavoidable. Without any assumption of "collapse", the *amplitudes* assigned to local measurements on either member of an entangled pair could be determined solely from amplitudes on locally-measurable variables in the past light cone--do you disagree? No, I don't disagree. But I also don't see the point -- the preparation of the singlet state is all that can be known about the states that either Alice or Bob have available for measurement. Addition information from the past light cone need be considered only if you want to pursue a "superdeterministic" theory in which A and B are not actually free to determine their measurement angles. That does not mean that there is actually a physical transfer of particles or waves FTL, it simply means that the state is a unity, and changing one part changes the whole state. That is the nature of quantum non-locality -- it does not have a local explanation, even a FTL explanation. There are no non-mathematical "explanations" for anything whatsoever in physics (obviously there can be explanations in words, but these are understood as shorthand for arguments that could be formalized mathematically). And in terms of mathematical physics, the "explanation" for a local physical fact about what's happening in one point in spacetime is just the mathematical function representing the "laws of physics" along with whatever initial boundary c
Re: Non-locality and MWI
On Mon, May 2, 2016 at 1:10 AM, Bruce Kellett wrote: > On 2/05/2016 1:31 pm, Jesse Mazer wrote: > > On Sun, May 1, 2016 at 8:49 PM, Bruce Kellett > wrote: > >> On 2/05/2016 7:52 am, Jesse Mazer wrote: >> >> On Fri, Apr 29, 2016 at 8:32 PM, Bruce Kellett < >> bhkell...@optusnet.com.au> wrote: >> >>> That is a semantic matter. There is a problem if one insists that >>> "non-local" means the propagation of a real physical influence (particle of >>> wave) faster-than-light. But "non-locality" in standard quantum usage means >>> the above -- the entangled state acts as a single physical unit even when >>> its components are widely separated. >> >> >> >> I agree it's a semantic matter, but your description of the "standard >> quantum usage" doesn't seem to be accurate. Among physicists, the standard >> understanding of "local" and "non-local" in the context of Bell's theorem >> and relativity is the one I cited earlier--a theory is "local" if and only >> if the function that gives you the value of local variables at any given >> point P in spacetime (or gives the best possible probabilistic prediction >> about their values, in the case of a non-deterministic theory) only >> requires as input the values of local variables at other points that lie >> within P's past light cone, whereas a "non-local" theory would be one where >> the function requires knowledge of variables at a spacelike separation from >> P to generate the best possible prediction. As I mentioned, I think this is >> explained most clearly in Bell's paper "La nouvelle cuisine" which you can >> find in the collection "Speakable and Unspeakable in Quantum Mechanics", >> and you can also find it discussed in other sources, >> http://arxiv.org/abs/0707.0401 for example. As for "acts as a single >> physical unit", that seems like a decidedly non-mathematical definition >> which physicists would steer clear of, unless you can provide a >> mathematical formalization or what you mean, or cite a mainstream source >> that provides one. >> >> >> I don't see any paper of the title you mention in my copy of "Speakable >> and Unspeakable in Quantum Mechanics", could you give a page number >> reference? >> > > > It's on p. 232 of the 2nd edition, chapter 24. > > > I have now looked at the paper by Norsen. It seems that the more detailed > definiton of locality does little more than remove the notion of > "superdeterminism" from the equation -- the idea that things in the common > past of A and B could conspire to give rise to the correlations. > The paper by Norsen at http://arxiv.org/pdf/0707.0401v3.pdf does mention the issue of ruling out superdeterminism, but that wasn't what I was referring to when I talked about the definition in La nouvelle cuisine which is repeated in Norsen's paper. Rather I was talking about equation 1 on page 4 whose physical meaning in terms of past light cones is show in Fig. 2 on the same page. Referring to the diagram and equation, b1 refers to the physical state of local variables in region 1, b2 refers to the physical state of local variables in another region 2 at a spacelike separation of 1, and B3 refers to some sufficiently detailed set of local states in region 3 which is in the past light cone of region 1, but entirely outside the past light cone of region 2. The idea is that by picking a sufficiently detailed set for your B3, you can have it so that once you know B3, additional knowledge of b2 is irrelevant to your prediction of what's going on in b1, i.e. you don't need anything outside the past light cone of 1 to make the best possible physical prediction about the physical facts in that region. So, nothing to do with superdeterminism, just a more formal statement of the idea I described earlier about the function for making predictions about a given region depending only on facts in the past light cone of that region. Jesse -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On Mon, May 2, 2016 at 12:13 AM, Bruce Kellett wrote: > > No, I disagree. The setting *b* has no effect on what happens at a remote > location is sufficiently precise to encapsulate exactly what physicists > mean by locality. In quantum field theory, this is generalized to the > notion of local causality, which is the statement that the commutators of > all spacelike separate variables vanish -- as you mention below. > And if you used full quantum description of the measuring apparatus and experimenter, and didn't assume any collapse on measurement, then there would in general be no single "setting b" in the region of spacetime where one experimenter was choosing a setting, but rather a superposition of different settings. Do you think your preferred definition can be meaningfully applied to this case, and if so how? > > My qualitative definition of non-locality is not non-standard -- it is the >> definition frequently used by Bell, and (almost) everyone else. Your >> definition seems to want to take account of some sort of hidden variables, >> such that the quantum state as written does not contain all the information >> about that state. >> > > > There are no hidden variables in the MWI (though the definition of > locality should be general enough to cover theories with hidden variables > as well as ones with no hidden variables, since Bell's theorem is meant to > rule out local realist theories of either type). The "quantum state as > written" does not give any definite outcomes of measurements, only a set of > amplitudes on different eigenvectors associated with particular > eigenvalues, which are understood as possible measurement results. > > > True, but not relevant for these purposes. I am not ruling out an > Everettian interpretation of the state vector -- my definition of locality > simply rules out faster than light (FTL) transfer of information. Given the > standard quantum treatment of the entangled singlet state, non-locality is > unavoidable. > Without any assumption of "collapse", the *amplitudes* assigned to local measurements on either member of an entangled pair could be determined solely from amplitudes on locally-measurable variables in the past light cone--do you disagree? > That does not mean that there is actually a physical transfer of particles > or waves FTL, it simply means that the state is a unity, and changing one > part changes the whole state. That is the nature of quantum non-locality -- > it does not have a local explanation, even a FTL explanation. > There are no non-mathematical "explanations" for anything whatsoever in physics (obviously there can be explanations in words, but these are understood as shorthand for arguments that could be formalized mathematically). And in terms of mathematical physics, the "explanation" for a local physical fact about what's happening in one point in spacetime is just the mathematical function representing the "laws of physics" along with whatever initial boundary conditions have to be fed into the function to generate the prediction about that local physical fact. If the boundary conditions are all confined to the past light cone, I would say there is nothing FTL in this mathematical explanation--you may disagree, but so far you have been unable to provide any alternate precisely-defined conditions for distinguishing locality from non-locality, ones which we could still obviously make sense of even if we didn't assume a unique real-valued measurement setting and measurement outcome. > And if you just want the amplitudes for locally-measurable quantities in a > given region of spacetime, in quantum field theory my understanding is that > you can determine this using only knowledge of amplitudes for > locally-measurable quantities in the past light cone of that region (I > don't understand the details, but this is supposed to have to do with the > fact that the commutators for spacelike-separated points always vanish). > Only if you assume there is an objective "collapse" of the wavefunction at > the point of measurement does the quantum formalism become incompatible > with locality in the light cone sense. > > > That is not correct. You have not given a local account in MWI either. > What does "account" mean? A mathematical description, or a conceptual explanation in the English language? > Your "light cone sense" of locality would only add something to the > traditional sense if the quantum state were not a complete description of > the system. In other words, a hidden variable theory. > I have no idea why you think this, and you haven't made any argument for it. Your traditional sense seems to be simply ill-defined if we assume a superposition of different detecter settings in a single location in spacetime, and a superposition of measurement results at another location, whereas the "light-cone sense" is still well-defined here since it can cover local variables of any kind, including a bundle of complex amplitudes a
Re: Non-locality and MWI
On 2/05/2016 1:31 pm, Jesse Mazer wrote: On Sun, May 1, 2016 at 8:49 PM, Bruce Kellett mailto:bhkell...@optusnet.com.au>> wrote: On 2/05/2016 7:52 am, Jesse Mazer wrote: On Fri, Apr 29, 2016 at 8:32 PM, Bruce Kellett mailto:bhkell...@optusnet.com.au>> wrote: That is a semantic matter. There is a problem if one insists that "non-local" means the propagation of a real physical influence (particle of wave) faster-than-light. But "non-locality" in standard quantum usage means the above -- the entangled state acts as a single physical unit even when its components are widely separated. I agree it's a semantic matter, but your description of the "standard quantum usage" doesn't seem to be accurate. Among physicists, the standard understanding of "local" and "non-local" in the context of Bell's theorem and relativity is the one I cited earlier--a theory is "local" if and only if the function that gives you the value of local variables at any given point P in spacetime (or gives the best possible probabilistic prediction about their values, in the case of a non-deterministic theory) only requires as input the values of local variables at other points that lie within P's past light cone, whereas a "non-local" theory would be one where the function requires knowledge of variables at a spacelike separation from P to generate the best possible prediction. As I mentioned, I think this is explained most clearly in Bell's paper "La nouvelle cuisine" which you can find in the collection "Speakable and Unspeakable in Quantum Mechanics", and you can also find it discussed in other sources, http://arxiv.org/abs/0707.0401 for example. As for "acts as a single physical unit", that seems like a decidedly non-mathematical definition which physicists would steer clear of, unless you can provide a mathematical formalization or what you mean, or cite a mainstream source that provides one. I don't see any paper of the title you mention in my copy of "Speakable and Unspeakable in Quantum Mechanics", could you give a page number reference? It's on p. 232 of the 2nd edition, chapter 24. I have now looked at the paper by Norsen. It seems that the more detailed definiton of locality does little more than remove the notion of "superdeterminism" from the equation -- the idea that things in the common past of A and B could conspire to give rise to the correlations. Bell rules this out: “An essential element in the reasoning here is that [aˆ] and [ˆb] are free variables. One canenvisage then theories in which there just are no free variables for the polarizer angles to be coupled to. In such ‘superdeterministic’ theories the apparent free will of experimenters, and any other apparent randomness, would be illusory. Perhaps such a theory could be both locally causal and in agreement with quantum mechanical predictions. However I do not expect to see a serious theory of this kind. I would expect a serious theory to permit ‘deterministic chaos’ or ‘pseudorandomness’, for complicated subsystems (e.g. computers) which would provide variables sufficiently free for the purpose at hand. But I do not have a theorem about that.”7 Quoted from the "La nouvelle cuisine" paper. Bell is quite clear in his opinion that orthodox QM is not a locally causal theory: “The theory requires a perfect correlation of [results] on the two sides. So specification of the result on one side permits a 100% confident prediction of the previously totally uncertain result on the other side. Now in ordinary quantum mechanics there just is nothing but the wavefunction for calculating probabilities. There is then no question of making the result on one side redundant on the other by more fully specifying events in some space-time region 3. We have a violation of local causality.”7 I don't think there is any case for me to answer - my informal definition of locality is perfectly adequate for the current purposes. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 2/05/2016 1:31 pm, Jesse Mazer wrote: On Sun, May 1, 2016 at 8:49 PM, Bruce Kellett mailto:bhkell...@optusnet.com.au>> wrote: On 2/05/2016 7:52 am, Jesse Mazer wrote: On Fri, Apr 29, 2016 at 8:32 PM, Bruce Kellett mailto:bhkell...@optusnet.com.au>> wrote: That is a semantic matter. There is a problem if one insists that "non-local" means the propagation of a real physical influence (particle of wave) faster-than-light. But "non-locality" in standard quantum usage means the above -- the entangled state acts as a single physical unit even when its components are widely separated. I agree it's a semantic matter, but your description of the "standard quantum usage" doesn't seem to be accurate. Among physicists, the standard understanding of "local" and "non-local" in the context of Bell's theorem and relativity is the one I cited earlier--a theory is "local" if and only if the function that gives you the value of local variables at any given point P in spacetime (or gives the best possible probabilistic prediction about their values, in the case of a non-deterministic theory) only requires as input the values of local variables at other points that lie within P's past light cone, whereas a "non-local" theory would be one where the function requires knowledge of variables at a spacelike separation from P to generate the best possible prediction. As I mentioned, I think this is explained most clearly in Bell's paper "La nouvelle cuisine" which you can find in the collection "Speakable and Unspeakable in Quantum Mechanics", and you can also find it discussed in other sources, http://arxiv.org/abs/0707.0401 for example. As for "acts as a single physical unit", that seems like a decidedly non-mathematical definition which physicists would steer clear of, unless you can provide a mathematical formalization or what you mean, or cite a mainstream source that provides one. I don't see any paper of the title you mention in my copy of "Speakable and Unspeakable in Quantum Mechanics", could you give a page number reference? It's on p. 232 of the 2nd edition, chapter 24. I only have access to the first edition -- this must refer to a later paper of Bell's. What I did find was chapter 8, "Locality in quantum mechanics: reply to critics" (pp. 63-66). In that chapter, Bell says: "...now we add the hypothesis of l/ocality/, that the setting *b* of a particular instrument has no effect on what happens, A, in a remote region, and likewise that *a* has no effect on B. With these /local/ forms, it is /not /possible to find functions A and B and a probability distribution /rho/ which give the correlations = -*a.b*." This is an informal statement of exactly the notion of locality or non-locality that I have been using all along. Your more convoluted statement may bear some relation to Bell's theory of local beables (chapter 7 of his book), but the complications are unnecessary -- the informal definition is the one most physicists would use in practice. I disagree, physicists generally only use informal definitions if it's obvious they could be formalized, or if they are *implied* by some more precise technical definition (the looser definition you mention above would be implied by the more precise one I mentioned, *if* one assumes there is a unique truth about the setting at b and the measurement A). No, I disagree. The setting *b* has no effect on what happens at a remote location is sufficiently precise to encapsulate exactly what physicists mean by locality. In quantum field theory, this is generalized to the notion of local causality, which is the statement that the commutators of all spacelike separate variables vanish -- as you mention below. If quantum mechanics is complete, then the current quantum state contains all the information about the system that is either available or relevant. Sure, if you include hidden variables, then you are saying that QM as currently formulated is incomplete. That may be the case, but even so, the given definition of locality still holds -- it is about FTL propagation of information, nothing else. My qualitative definition of non-locality is not non-standard -- it is the definition frequently used by Bell, and (almost) everyone else. Your definition seems to want to take account of some sort of hidden variables, such that the quantum state as written does not contain all the information about that state. There are no hidden variables in the MWI (though the definition of locality should be general enough to cover theories with hidden variables as well as ones with no hidden variables, since Bell's theorem is meant to rule out local realist theories of either type). The "quantum state as written" does not
Re: Non-locality and MWI
On Sun, May 1, 2016 at 8:49 PM, Bruce Kellett wrote: > On 2/05/2016 7:52 am, Jesse Mazer wrote: > > On Fri, Apr 29, 2016 at 8:32 PM, Bruce Kellett > wrote: > >> That is a semantic matter. There is a problem if one insists that >> "non-local" means the propagation of a real physical influence (particle of >> wave) faster-than-light. But "non-locality" in standard quantum usage means >> the above -- the entangled state acts as a single physical unit even when >> its components are widely separated. > > > > I agree it's a semantic matter, but your description of the "standard > quantum usage" doesn't seem to be accurate. Among physicists, the standard > understanding of "local" and "non-local" in the context of Bell's theorem > and relativity is the one I cited earlier--a theory is "local" if and only > if the function that gives you the value of local variables at any given > point P in spacetime (or gives the best possible probabilistic prediction > about their values, in the case of a non-deterministic theory) only > requires as input the values of local variables at other points that lie > within P's past light cone, whereas a "non-local" theory would be one where > the function requires knowledge of variables at a spacelike separation from > P to generate the best possible prediction. As I mentioned, I think this is > explained most clearly in Bell's paper "La nouvelle cuisine" which you can > find in the collection "Speakable and Unspeakable in Quantum Mechanics", > and you can also find it discussed in other sources, > http://arxiv.org/abs/0707.0401 for example. As for "acts as a single > physical unit", that seems like a decidedly non-mathematical definition > which physicists would steer clear of, unless you can provide a > mathematical formalization or what you mean, or cite a mainstream source > that provides one. > > > I don't see any paper of the title you mention in my copy of "Speakable > and Unspeakable in Quantum Mechanics", could you give a page number > reference? > It's on p. 232 of the 2nd edition, chapter 24. > What I did find was chapter 8, "Locality in quantum mechanics: reply to > critics" (pp. 63-66). In that chapter, Bell says: "...now we add the > hypothesis of l*ocality*, that the setting *b* of a particular instrument > has no effect on what happens, A, in a remote region, and likewise that > *a* has no effect on B. With these *local* forms, it is *not *possible > to find functions A and B and a probability distribution *rho* which give > the correlations = -*a.b*." > > This is an informal statement of exactly the notion of locality or > non-locality that I have been using all along. Your more convoluted > statement may bear some relation to Bell's theory of local beables (chapter > 7 of his book), but the complications are unnecessary -- the informal > definition is the one most physicists would use in practice. > I disagree, physicists generally only use informal definitions if it's obvious they could be formalized, or if they are *implied* by some more precise technical definition (the looser definition you mention above would be implied by the more precise one I mentioned, *if* one assumes there is a unique truth about the setting at b and the measurement A). > My qualitative definition of non-locality is not non-standard -- it is the > definition frequently used by Bell, and (almost) everyone else. Your > definition seems to want to take account of some sort of hidden variables, > such that the quantum state as written does not contain all the information > about that state. > There are no hidden variables in the MWI (though the definition of locality should be general enough to cover theories with hidden variables as well as ones with no hidden variables, since Bell's theorem is meant to rule out local realist theories of either type). The "quantum state as written" does not give any definite outcomes of measurements, only a set of amplitudes on different eigenvectors associated with particular eigenvalues, which are understood as possible measurement results. And if you just want the amplitudes for locally-measurable quantities in a given region of spacetime, in quantum field theory my understanding is that you can determine this using only knowledge of amplitudes for locally-measurable quantities in the past light cone of that region (I don't understand the details, but this is supposed to have to do with the fact that the commutators for spacelike-separated points always vanish). Only if you assume there is an objective "collapse" of the wavefunction at the point of measurement does the quantum formalism become incompatible with locality in the light cone sense. Jesse -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list
Re: Non-locality and MWI
On 2/05/2016 7:52 am, Jesse Mazer wrote: On Fri, Apr 29, 2016 at 8:32 PM, Bruce Kellett mailto:bhkell...@optusnet.com.au>> wrote: That is a semantic matter. There is a problem if one insists that "non-local" means the propagation of a real physical influence (particle of wave) faster-than-light. But "non-locality" in standard quantum usage means the above -- the entangled state acts as a single physical unit even when its components are widely separated. I agree it's a semantic matter, but your description of the "standard quantum usage" doesn't seem to be accurate. Among physicists, the standard understanding of "local" and "non-local" in the context of Bell's theorem and relativity is the one I cited earlier--a theory is "local" if and only if the function that gives you the value of local variables at any given point P in spacetime (or gives the best possible probabilistic prediction about their values, in the case of a non-deterministic theory) only requires as input the values of local variables at other points that lie within P's past light cone, whereas a "non-local" theory would be one where the function requires knowledge of variables at a spacelike separation from P to generate the best possible prediction. As I mentioned, I think this is explained most clearly in Bell's paper "La nouvelle cuisine" which you can find in the collection "Speakable and Unspeakable in Quantum Mechanics", and you can also find it discussed in other sources, http://arxiv.org/abs/0707.0401 for example. As for "acts as a single physical unit", that seems like a decidedly non-mathematical definition which physicists would steer clear of, unless you can provide a mathematical formalization or what you mean, or cite a mainstream source that provides one. I don't see any paper of the title you mention in my copy of "Speakable and Unspeakable in Quantum Mechanics", could you give a page number reference? What I did find was chapter 8, "Locality in quantum mechanics: reply to critics" (pp. 63-66). In that chapter, Bell says: "...now we add the hypothesis of l/ocality/, that the setting *b* of a particular instrument has no effect on what happens, A, in a remote region, and likewise that *a* has no effect on B. With these /local/ forms, it is /not /possible to find functions A and B and a probability distribution /rho/ which give the correlations = -*a.b*." This is an informal statement of exactly the notion of locality or non-locality that I have been using all along. Your more convoluted statement may bear some relation to Bell's theory of local beables (chapter 7 of his book), but the complications are unnecessary -- the informal definition is the one most physicists would use in practice. Bruno should be aware that in the discussion you and I had earlier, you used this sort of qualitative non-standard definition to argue even if the function giving values of physical variables at each point *does* depend solely on data from the past light cone, that is "irrelevant" to deciding whether the theory is "local" in your sense, presumably because you think there can be qualitative features of the function itself that can make it "non-local" for reasons unrelated to the question of what data the function takes as input. My qualitative definition of non-locality is not non-standard -- it is the definition frequently used by Bell, and (almost) everyone else. Your definition seems to want to take account of some sort of hidden variables, such that the quantum state as written does not contain all the information about that state. Since the quantum state is taken to be a complete description, its past history over the whole of its light cone is truly irrelevant. Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On Fri, Apr 29, 2016 at 8:32 PM, Bruce Kellett wrote: > > That is a semantic matter. There is a problem if one insists that > "non-local" means the propagation of a real physical influence (particle of > wave) faster-than-light. But "non-locality" in standard quantum usage means > the above -- the entangled state acts as a single physical unit even when > its components are widely separated. I agree it's a semantic matter, but your description of the "standard quantum usage" doesn't seem to be accurate. Among physicists, the standard understanding of "local" and "non-local" in the context of Bell's theorem and relativity is the one I cited earlier--a theory is "local" if and only if the function that gives you the value of local variables at any given point P in spacetime (or gives the best possible probabilistic prediction about their values, in the case of a non-deterministic theory) only requires as input the values of local variables at other points that lie within P's past light cone, whereas a "non-local" theory would be one where the function requires knowledge of variables at a spacelike separation from P to generate the best possible prediction. As I mentioned, I think this is explained most clearly in Bell's paper "La nouvelle cuisine" which you can find in the collection "Speakable and Unspeakable in Quantum Mechanics", and you can also find it discussed in other sources, http://arxiv.org/abs/0707.0401 for example. As for "acts as a single physical unit", that seems like a decidedly non-mathematical definition which physicists would steer clear of, unless you can provide a mathematical formalization or what you mean, or cite a mainstream source that provides one. Bruno should be aware that in the discussion you and I had earlier, you used this sort of qualitative non-standard definition to argue even if the function giving values of physical variables at each point *does* depend solely on data from the past light cone, that is "irrelevant" to deciding whether the theory is "local" in your sense, presumably because you think there can be qualitative features of the function itself that can make it "non-local" for reasons unrelated to the question of what data the function takes as input. Jesse -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On Wed, Apr 27, 2016 at 7:55 PM, Bruce Kellett wrote: > > Baez's crackpot index is good fun, but it does have some amusing side > effects: > 37. 50 points for claiming you have a revolutionary theory but giving no > concrete testable predictions. > does seem to do considerable damage to current proponents of string > theory: they have the highest possible score on the crackpot index! > Many would say, and I agree, that string "theory" is a work in progress and it's not a theory yet, it's a theory for a theory. Incidentally Richard Feynman said string theory DID make a testable prediction and it failed the test, it predicted space would have 10 dimensions not 3, so they had to stick in a bunch of fudge factors about shrinking 7 dimensions and entangle them in 10^500 different ways. Still, string theory did say there must be a spin 2 particle that sounds very much like the graviton so maybe there is hope. John K Clark -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 29/04/2016 9:09 pm, Bruno Marchal wrote: On 28 Apr 2016, at 03:33, Bruce Kellett wrote: On 27/04/2016 4:57 pm, Bruno Marchal wrote: On 27 Apr 2016, at 06:49, Bruce Kellett wrote: On 27/04/2016 1:51 pm, Brent Meeker wrote: That's pretty much the many-universes model that Bruno proposes. But it's non-local in the sense that the "matching scheme" must take account of which measurements are compatible, i.e. it "knows" the results even while they are spacelike separated. Exactly, the model assumes the results it is trying to get. It is not a local physical model because the statistics do not originate locally. The statistic did originate locally. Alice and Bob did prepare the singlet state locally, and then travel away. That is not strictly correct. The singlet state is conventionally prepared centrally between A and B so that the measurements can be made at spacelike separation. That would not be possible if A and B jointly prepare the state then move away. The measurement? OK. Not the preparation. They are in infinitely many worlds, and in each with opposite spin. There are only two possible spin states for each -- so there are really only two distinct possible worlds. Multiplying copies of these two does not seem to accomplish much. There is an infinity of possible states for each. There is an infinity of possible distinct possible worlds. In each one A's and B's particle spin are opposite/correlated, but neither Alice nor Bob can know which one. I think you are getting confused by the basis problem again. The cos^2(theta) is given by the math of the 1/sqrt(2)AB(I+>I-> - I->I+>)) = 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+>. With your explanation to Jesse, I keep the feeling that you talk like if Alice or Bob reduce the wave after their measurement, but they just localize themselves in the relative branches. Certainly, the cos^2(theta/2) comes from applying the standard quantum rules to the singlet state |psi> = (|+>|-> - |->|+>)/sqrt(2) (adding AB to this state adds nothing). We need them to get all the statistics correct. I think it would be instructive to actually go through the usual quantum derivation of the correlations because what you call "reducing the wave after the measurement" is actually the result of applying the standard quantum rules. It has nothing to do with so-called 'collapse' interpretations: it is simply in the theory. Well, either the meaurement give specific outcome, or, if there is no physical collapse it is only an entanglement between A (or B) with the singlet state. That is why A and B are needed in the derivation. A measurement results in an entanglement between the state and the observer. But in order for the observer to see only one result (and not a superposition) you need the projection postulate. That is decoherence, not a rejection of many worlds. Quantum rules for measurement say that the initial state can be expanded in the basis corresponding to the particular measurement in question (contextuality). That is what the state |psi> above is -- the quantum expansion of the singlet state in the basis in which say Alice is doing her measurement. OK, but that state does not represent two possible worlds. It looks like that for Alice because she has decided to make the measurement "in that base", but, as we know, the correlation does not depend on the choice of Alice's measurement. She will just entangled herself with the singlet state, whatever the base or measuring apparatus is. Quantum rules then say that the result of the measurement (after decoherence has fully operated) Decoherence is only the contagion of the superposition to the observer and/or his/her environment. It does not lead to a classical universe. That is only what the infinitely many Alice will phenomenologivally realize. Decoherence is the basis for the (apparent) emergence of the classical from the quantum. Decoherence allows coarse-graining, partial tracing over environmental variables, and the other things that enable us to get definite experimental results. is one of the eigenstates in the expansion, and the measurement result is the corresponding eigenvalue. In our case, there are two possibilities for Alice after her measurement is complete: result '+', with corresponding eigenstate |+>|->, or '-', with corresponding eigenstate |->|+>. There are no other possibilities, and Alice has a 50% chance of obtaining either result, or of being in the corresponding branch of the evolved wave function. That is correct phenomenologically. But QM-without collapse just say that we get a new Ipsi> equal to A(|+>|-> - |->|+>)/sqrt(2) = (A|+>|-> - A|->|+>)/sqrt(2). At no moment is Alice in front of only |+>|-> or |->|+>. The singlet state never disappear. That is the basis of your confusion. What you are saying, in effect, is that the state is not reduced to the eigenvector corresponding to the obtained eigenvalue after meas
Re: R: Re: R: Re: Non-locality and MWI
Here is a paper from the Journal of Cosmology, written by a comp sci professor at the University of Warwick, UK. I like it because of its logical flow, and, of course, no idea if its plausible, but it does correlate with MWI and the wave function, observers, and all that fun stuff of physics and computationalism. Anyone want to test drive this hypothesis and the logics? I like it, but don't know if this helps us? http://webcache.googleusercontent.com/search?q=cache:gSwPx43hKBsJ:journalofcosmology.com/JOC24/Forrest_Paper_2.pdf+&cd=2&hl=en&ct=clnk&gl=us -Original Message- From: Bruno Marchal To: everything-list Sent: Fri, Apr 29, 2016 8:19 am Subject: Re: R: Re: R: Re: Non-locality and MWI On 29 Apr 2016, at 09:41, 'scerir' via Everything List wrote: Da: spudboy100 via Everything List Data: 28/04/2016 21.46 A: Ogg: Re: R: Re: Non-locality and MWI Is there any practical technical use for MWI as applied science. Just asking? Dunno. Quantum computers? Maybe there is a Many Interpretations Conjecture :-) Interpretations of quantum mechanics, unlike Gods, are not jealous, and thus it is safe to believe in more than one at the same time. Well, only because we tolerate non-sense in religion. I am not sure we can do that for a long time. So if the many-worlds interpretation makes it easier to think about the research you're doing in April, and the Copenhagen interpretation makes it easier to think about the research you're doing in June, the Copenhagen interpretation is not going to smite you for praying to the many-worlds interpretation. At least I hope it won't, because otherwise I'm in big trouble. ---Peter Shor Same with religion. We need only to have, relatively to the facts, consistent views, with ourselves, and eventually with each others. I believe in every interpretation of quantum mechanics to the extent it points out the problem, and disbelieve in every interpretation to the extent it claims to have solved it. Good! I believe the same for the religions. Bruno --Scott Aaronson -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI
Ok, thanks. Yes, I read Deutsches interp some years back. I also like his later, Constructor theory, but this is sort of off topic. -Original Message- From: Bruno Marchal To: everything-list Sent: Fri, Apr 29, 2016 8:09 am Subject: Re: R: Re: Non-locality and MWI On 29 Apr 2016, at 04:16, Stathis Papaioannou wrote: On 29 April 2016 at 07:27, spudboy100 via Everything List wrote: Hah! Well somebody will get rich of we take the Everett stuff as fact. Not likely myself for all this. Sincerely, Your humble clone Kill off the poor ones and then you're sure to be the rich one. That seems to me like cutting of the right part of a wooden rule to get only a left part. Spudboy, MWI is only an attempt to make sense of QM. Its practical application is the same as QM. Now David Deustch would mention Quantum computer, that he discovered thanks to the MWI. MWI = taken the reality of the superposed states seriously, as already the two slits experiment with one photon illustrates that we should do. For me, but also for Deutsch and for Everett MWI = QM-without collapse. Everett's published paper, even its long text, does not mention "many world" but only a new theory: the old one minus the physical collapse of the wave. Bruno -- Stathis Papaioannou -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: R: Re: Non-locality and MWI
On 29 Apr 2016, at 09:41, 'scerir' via Everything List wrote: Da: spudboy100 via Everything List Data: 28/04/2016 21.46 A: Ogg: Re: R: Re: Non-locality and MWI Is there any practical technical use for MWI as applied science. Just asking? Dunno. Quantum computers? Maybe there is a Many Interpretations Conjecture :-) Interpretations of quantum mechanics, unlike Gods, are not jealous, and thus it is safe to believe in more than one at the same time. Well, only because we tolerate non-sense in religion. I am not sure we can do that for a long time. So if the many-worlds interpretation makes it easier to think about the research you're doing in April, and the Copenhagen interpretation makes it easier to think about the research you're doing in June, the Copenhagen interpretation is not going to smite you for praying to the many-worlds interpretation. At least I hope it won't, because otherwise I'm in big trouble. ---Peter Shor Same with religion. We need only to have, relatively to the facts, consistent views, with ourselves, and eventually with each others. I believe in every interpretation of quantum mechanics to the extent it points out the problem, and disbelieve in every interpretation to the extent it claims to have solved it. Good! I believe the same for the religions. Bruno --Scott Aaronson -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI
On 29 Apr 2016, at 04:16, Stathis Papaioannou wrote: On 29 April 2016 at 07:27, spudboy100 via Everything List > wrote: Hah! Well somebody will get rich of we take the Everett stuff as fact. Not likely myself for all this. Sincerely, Your humble clone Kill off the poor ones and then you're sure to be the rich one. That seems to me like cutting of the right part of a wooden rule to get only a left part. Spudboy, MWI is only an attempt to make sense of QM. Its practical application is the same as QM. Now David Deustch would mention Quantum computer, that he discovered thanks to the MWI. MWI = taken the reality of the superposed states seriously, as already the two slits experiment with one photon illustrates that we should do. For me, but also for Deutsch and for Everett MWI = QM-without collapse. Everett's published paper, even its long text, does not mention "many world" but only a new theory: the old one minus the physical collapse of the wave. Bruno -- Stathis Papaioannou -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI
Ah! Now you speak of the policies of the Ruling Class, which need no physics, or many worlds, just self centered behavior. Also, chances are via Hugh Everett, because I am not already rich, I am one of the others, as being a rich clone is not my wave function. -Original Message- From: Stathis Papaioannou To: everything-list Sent: Thu, Apr 28, 2016 10:17 pm Subject: Re: R: Re: Non-locality and MWI On 29 April 2016 at 07:27, spudboy100 via Everything List wrote: Hah! Well somebody will get rich of we take the Everett stuff as fact. Not likely myself for all this. Sincerely, Your humble clone Kill off the poor ones and then you're sure to be the rich one. -- Stathis Papaioannou -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 28 Apr 2016, at 03:33, Bruce Kellett wrote: On 27/04/2016 4:57 pm, Bruno Marchal wrote: On 27 Apr 2016, at 06:49, Bruce Kellett wrote: On 27/04/2016 1:51 pm, Brent Meeker wrote: That's pretty much the many-universes model that Bruno proposes. But it's non-local in the sense that the "matching scheme" must take account of which measurements are compatible, i.e. it "knows" the results even while they are spacelike separated. Exactly, the model assumes the results it is trying to get. It is not a local physical model because the statistics do not originate locally. The statistic did originate locally. Alice and Bob did prepare the singlet state locally, and then travel away. That is not strictly correct. The singlet state is conventionally prepared centrally between A and B so that the measurements can be made at spacelike separation. That would not be possible if A and B jointly prepare the state then move away. The measurement? OK. Not the preparation. They are in infinitely many worlds, and in each with opposite spin. There are only two possible spin states for each -- so there are really only two distinct possible worlds. Multiplying copies of these two does not seem to accomplish much. There is an infinity of possible states for each. There is an infinity of possible distinct possible worlds. In each one A's and B's particle spin are opposite/correlated, but neither Alice nor Bob can know which one. The cos^2(theta) is given by the math of the 1/sqrt(2)AB(I+>I-> - I- >I+>)) = 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+>. With your explanation to Jesse, I keep the feeling that you talk like if Alice or Bob reduce the wave after their measurement, but they just localize themselves in the relative branches. Certainly, the cos^2(theta/2) comes from applying the standard quantum rules to the singlet state |psi> = (|+>|-> - |->|+>)/sqrt(2) (adding AB to this state adds nothing). We need them to get all the statistics correct. I think it would be instructive to actually go through the usual quantum derivation of the correlations because what you call "reducing the wave after the measurement" is actually the result of applying the standard quantum rules. It has nothing to do with so- called 'collapse' interpretations: it is simply in the theory. Well, either the meaurement give specific outcome, or, if there is no physical collapse it is only an entanglement between A (or B) with the singlet state. That is why A and B are needed in the derivation. Quantum rules for measurement say that the initial state can be expanded in the basis corresponding to the particular measurement in question (contextuality). That is what the state |psi> above is -- the quantum expansion of the singlet state in the basis in which say Alice is doing her measurement. OK, but that state does not represent two possible worlds. It looks like that for Alice because she has decided to make the measurement "in that base", but, as we know, the correlation does not depend on the choice of Alice's measurement. She will just entangled herself with the singlet state, whatever the base or measuring apparatus is. Quantum rules then say that the result of the measurement (after decoherence has fully operated) Decoherence is only the contagion of the superposition to the observer and/or his/her environment. It does not lead to a classical universe. That is only what the infinitely many Alice will phenomenologivally realize. is one of the eigenstates in the expansion, and the measurement result is the corresponding eigenvalue. In our case, there are two possibilities for Alice after her measurement is complete: result '+', with corresponding eigenstate |+>|->, or '-', with corresponding eigenstate |->|+>. There are no other possibilities, and Alice has a 50% chance of obtaining either result, or of being in the corresponding branch of the evolved wave function. That is correct phenomenologically. But QM-without collapse just say that we get a new Ipsi> equal to A(|+>|-> - |->|+>)/sqrt(2) = (A|+>|-> - A|->|+>)/sqrt(2). At no moment is Alice in front of only |+>|-> or |->|+>. The singlet state never disappear. The question now arises as to how the formalism describes Bob's measurement, assuming that it follows that of Alice (there will always be a Lorentz frame in which that is true for spacelike separations. For timelike separations, it is either true, or we reverse the A/B labels so that it is true.) Since the description of the state does not depend on the separation between A and B, after A gets '+' and her eigenstate is |+>|->, Bob must measure the state |- > in the direction of his magnet. To get the relative probabilities for his results, we must rotate the eigenfunction from Alice's basis to the basis appropriate for Bob's measurement. This is the standard rotation of a spinor,
R: Re: R: Re: Non-locality and MWI
Da: spudboy100 via Everything List Data: 28/04/2016 21.46 A: Ogg: Re: R: Re: Non-locality and MWI Is there any practical technical use for MWI as applied science. Just asking? Dunno. Quantum computers? Maybe there is a Many Interpretations Conjecture :-) Interpretations of quantum mechanics, unlike Gods, are not jealous, and thus it is safe to believe in more than one at the same time. So if the many-worlds interpretation makes it easier to think about the research you're doing in April, and the Copenhagen interpretation makes it easier to think about the research you're doing in June, the Copenhagen interpretation is not going to smite you for praying to the many-worlds interpretation. At least I hope it won't, because otherwise I'm in big trouble. ---Peter Shor I believe in every interpretation of quantum mechanics to the extent it points outthe problem, and disbelieve in every interpretation to the extent it claims to have solved it.--Scott Aaronson -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI
On 29 April 2016 at 07:27, spudboy100 via Everything List < everything-list@googlegroups.com> wrote: > Hah! Well somebody will get rich of we take the Everett stuff as fact. Not > likely myself for all this. > > Sincerely, > Your humble clone > Kill off the poor ones and then you're sure to be the rich one. -- Stathis Papaioannou -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI
Hah! Well somebody will get rich of we take the Everett stuff as fact. Not likely myself for all this. Sincerely, Your humble clone -Original Message- From: Brent Meeker To: everything-list Sent: Thu, Apr 28, 2016 5:17 pm Subject: Re: R: Re: Non-locality and MWI You can try quantum suicide to get rich (c.f. "Schrondinger'sRabbits" by Colin Bruce). Brent On 4/28/2016 12:46 PM, spudboy100 via Everything List wrote: Is there anypractical technical use for MWI as applied science. Just asking? -Original Message- From: 'scerir' via Everything List To: everything-list Sent: Thu, Apr 28, 2016 3:24 pm Subject: R: Re: Non-locality and MWI BTW. Frank Wilczek: 'Entanglement Made Simple' Quantum entanglement is thought to be one of the trickiest concepts in science, but the core issues are simple. And once understood, entanglement opens up a richer understanding of concepts such as the “many worlds” of quantum theory. https://www.quantamagazine.org/20160428-entanglement-made-simple/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI
You can try quantum suicide to get rich (c.f. "Schrondinger's Rabbits" by Colin Bruce). Brent On 4/28/2016 12:46 PM, spudboy100 via Everything List wrote: Is there any practical technical use for MWI as applied science. Just asking? -Original Message- From: 'scerir' via Everything List To: everything-list Sent: Thu, Apr 28, 2016 3:24 pm Subject: R: Re: Non-locality and MWI BTW. Frank Wilczek: 'Entanglement Made Simple' Quantum entanglement is thought to be one of the trickiest concepts in science, but the core issues are simple. And once understood, entanglement opens up a richer understanding of concepts such as the “many worlds” of quantum theory. https://www.quantamagazine.org/20160428-entanglement-made-simple/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com <mailto:list+unsubscr...@googlegroups.com>. To post to this group, send email to everything-list@googlegroups.com <mailto:l...@googlegroups.com>. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com <mailto:everything-list+unsubscr...@googlegroups.com>. To post to this group, send email to everything-list@googlegroups.com <mailto:everything-list@googlegroups.com>. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: R: Re: Non-locality and MWI
Is there any practical technical use for MWI as applied science. Just asking? -Original Message- From: 'scerir' via Everything List To: everything-list Sent: Thu, Apr 28, 2016 3:24 pm Subject: R: Re: Non-locality and MWI BTW. Frank Wilczek: 'Entanglement Made Simple' Quantum entanglement is thought to be one of the trickiest concepts in science, but the core issues are simple. And once understood, entanglement opens up a richer understanding of concepts such as the “many worlds” of quantum theory. https://www.quantamagazine.org/20160428-entanglement-made-simple/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
R: Re: Non-locality and MWI
BTW. Frank Wilczek: 'Entanglement Made Simple' Quantum entanglement is thought to be one of the trickiest concepts in science, but the core issues are simple. And once understood, entanglement opens up a richer understanding of concepts such as the “many worlds” of quantum theory. https://www.quantamagazine.org/20160428-entanglement-made-simple/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On 27/04/2016 4:57 pm, Bruno Marchal wrote: On 27 Apr 2016, at 06:49, Bruce Kellett wrote: On 27/04/2016 1:51 pm, Brent Meeker wrote: That's pretty much the many-universes model that Bruno proposes. But it's non-local in the sense that the "matching scheme" must take account of which measurements are compatible, i.e. it "knows" the results even while they are spacelike separated. Exactly, the model assumes the results it is trying to get. It is not a local physical model because the statistics do not originate locally. The statistic did originate locally. Alice and Bob did prepare the singlet state locally, and then travel away. That is not strictly correct. The singlet state is conventionally prepared centrally between A and B so that the measurements can be made at spacelike separation. That would not be possible if A and B jointly prepare the state then move away. They are in infinitely many worlds, and in each with opposite spin. There are only two possible spin states for each -- so there are really only two distinct possible worlds. Multiplying copies of these two does not seem to accomplish much. The cos^2(theta) is given by the math of the 1/sqrt(2)AB(I+>I-> - I->I+>)) = 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+>. With your explanation to Jesse, I keep the feeling that you talk like if Alice or Bob reduce the wave after their measurement, but they just localize themselves in the relative branches. Certainly, the cos^2(theta/2) comes from applying the standard quantum rules to the singlet state |psi> = (|+>|-> - |->|+>)/sqrt(2) (adding AB to this state adds nothing). I think it would be instructive to actually go through the usual quantum derivation of the correlations because what you call "reducing the wave after the measurement" is actually the result of applying the standard quantum rules. It has nothing to do with so-called 'collapse' interpretations: it is simply in the theory. Quantum rules for measurement say that the initial state can be expanded in the basis corresponding to the particular measurement in question (contextuality). That is what the state |psi> above is -- the quantum expansion of the singlet state in the basis in which say Alice is doing her measurement. Quantum rules then say that the result of the measurement (after decoherence has fully operated) is one of the eigenstates in the expansion, and the measurement result is the corresponding eigenvalue. In our case, there are two possibilities for Alice after her measurement is complete: result '+', with corresponding eigenstate |+>|->, or '-', with corresponding eigenstate |->|+>. There are no other possibilities, and Alice has a 50% chance of obtaining either result, or of being in the corresponding branch of the evolved wave function. The question now arises as to how the formalism describes Bob's measurement, assuming that it follows that of Alice (there will always be a Lorentz frame in which that is true for spacelike separations. For timelike separations, it is either true, or we reverse the A/B labels so that it is true.) Since the description of the state does not depend on the separation between A and B, after A gets '+' and her eigenstate is |+>|->, Bob must measure the state |-> in the direction of his magnet. To get the relative probabilities for his results, we must rotate the eigenfunction from Alice's basis to the basis appropriate for Bob's measurement. This is the standard rotation of a spinor, given by |-> = sin(theta/2)|+'> -i cos(theta/2)|-'> Applying the standard quantum rules to this state, Bob has a probability of sin^2(theta/2) of obtaining a '+' result, and a probability of cos^2(theta/2) of obtaining a '-' result. Using test values for the relative orientation, theta, we get the usual results. For theta = 0º, Bob has probability 0 of obtaining '+', and probability 1 of obtaining '-'. For 90º orientation, the probabilities for '+' and '-' are both 0.5. For a relative orientation of 120º, Bob's probability of getting '+' is 0.75 and the probability of getting '-' is 0.25. And so on for the familiar results. This is not controversial, and the result depends only on the standard rules of quantum mechanics. The problem of interpretation, of course, is that since Alice and Bob are at different locations, and the state they are measuring is independent of separation, there is an intrinsic non-locality implied by the standard calculation. If you take out the quantum rule that the result of a measurement is, after decoherence, reduction to an eigenstate with the corresponding eigenvalue, you take away an essential ingredient of the quantum derivation, and leave Bob's measurement as being completely independent of that of Alice, so the only possible results for Bob are '+' and '-' with equal probability, whatever the orientation of his magnet. Any account that deviates from this is no longer a standard quantum account becau
Re: Non-locality and MWI
On 27/04/2016 5:24 pm, Jesse Mazer wrote: (Read a bunch of physicists getting philosophical about what their field is all about, and you'll find it's a very widely-held sentiment that physics is generally not be concerned with non-mathematical explanations for physical laws--the semi-famous 'crackpot index' at http://math.ucr.edu/home/baez/crackpot.html , concocted by physicist John Baez, even awards crackpot points to anyone who complains that even if a theory 'predicts phenomena correctly, it doesn't explain "why" they occur, or fails to provide a "mechanism".') Baez's crackpot index is good fun, but it does have some amusing side effects: 37. 50 points for claiming you have a revolutionary theory but giving no concrete testable predictions. does seem to do considerable damage to current proponents of string theory: they have the highest possible score on the crackpot index! Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
Re: Non-locality and MWI
On Wed, Apr 27, 2016 at 2:35 AM, Bruce Kellett wrote: > On 27/04/2016 4:13 pm, Jesse Mazer wrote: > > On Wed, Apr 27, 2016 at 1:40 AM, Bruce Kellett > wrote: > >> On 27/04/2016 3:22 pm, Jesse Mazer wrote: >> >> On Wed, Apr 27, 2016 at 12:47 AM, Bruce Kellett < >> bhkell...@optusnet.com.au> wrote: >> >>> Your simulation assumes the quantum mechanical results. In other words, >>> it assumes non-locality in order to calculate the statistics. Where does >>> the cos^2(theta/2) come from in your analysis? >>> >> >> The question I asked you was whether you thought you could definitively >> disprove the idea that all the observable statistics of QM could be >> reproduced by rules that are "local" in the specific narrow sense I had >> described to you--remember all that stuff about having computers >> determining what the value of local variables at each point in spacetime >> should be, using only information about the value of local variables in the >> past light cone of that point, plus the general rules programmed into them >> (which take that information about the past light cone as input, and spit >> out the value of local variables at that point as output)? This is a narrow >> and mathematically well-defined question (and is based specifically on how >> Bell defined 'locality'), it's completely irrelevant to the question >> whether or not the *idea* for the rules that I programmed into the >> computers that perform these local calculations came from looking at some >> equations that are written in a 'non-local' way (i.e., the equations >> generate their predictions by evolving a single 'state vector' for the >> entire spatially-distributed system). Do you understand this distinction >> between the narrow, well-defined definition of "local rules" (if you're >> unclear on what I mean here, please ask), and broader questions about what >> inspired the rules themselves? And are you claiming that even if we >> restrict our attention to the narrow definition of "local rules", you can >> still say with 100% certainty that no such "local rules" can accurately >> reproduce all the predictions about measurement outcomes made by QM? >> >> >> Your question, as outlined above, is completely devoid of interest to me >> as a physicist. I am interested in physical models that give an insight >> into how things come about. >> >> And yes, I am 100% certain that local rules, with local models for >> deciding what statistics should be reproduced to mimic quantum results on >> entangled systems, are impossible. >> > > And are you 100% certain of that last statement even if we define "local > rules" in the specific narrow sense I have described? Your comment that my > question concerning this narrow definition of locality is 'devoid of > interest' to you makes it unclear whether you were actually willing to > stick to the narrow definition in addressing my question, as I had > requested. > > > It is of no interest. You, and Rubin, advertised your work as a local > explanation of the EPR statistics. On detailed examination and pressing, > you admit that this is not the case > No, we use a definition of "locality" where it *is* the case, a mathematical definition that seems to correspond to how pretty much all mainstream physicists use the term "locality". You seem to say that even if a function takes as input only variables from the past light cone of a region to generate predictions about the values of variables within that region, it can be non-local because of something to do with where the idea for the function itself came from, a fuzzy notion that doesn't seem like it's likely to have any clear mathematical definition (if you think it can, please provide a general set of mathematical criteria for deciding whether some arbitrary mathematical function for generating predictions from boundary conditions is 'local', such that even a function that only uses variables in the past light cone as input may still fail to qualify as local). And since you answer my direct request to address my question with "it is of no interest", should I presume you are just refusing to answer the question I asked? Generally when people refuse to answer straightforward questions I take that as a sign they are not really interested in making a good-faith effort at mutual understanding, on figuring out what points we can (grudgingly) agree on as well as where we disagree (as opposed to just making a rhetorical case for a preferred view, or against a disliked view). So if you are indeed refusing outright to address this--even though this point about the possibility of a 'local' version of QM in this specific narrow sense is the central point *I* have been trying to argue this whole time--then I think I will bow out of our discussion here. > > Richard Feynman was frequently a bit "over the top" in his popular > accounts of physics. He is unkind to Newton, since the 1/r^2 form of the > law of gravitation follows simply from spherical symmetry and cons
Re: Non-locality and MWI
On 27 Apr 2016, at 08:35, Bruce Kellett wrote: On 27/04/2016 4:13 pm, Jesse Mazer wrote: On Wed, Apr 27, 2016 at 1:40 AM, Bruce Kellett > wrote: On 27/04/2016 3:22 pm, Jesse Mazer wrote: On Wed, Apr 27, 2016 at 12:47 AM, Bruce Kellett > wrote: Your simulation assumes the quantum mechanical results. In other words, it assumes non-locality in order to calculate the statistics. Where does the cos^2(theta/2) come from in your analysis? The question I asked you was whether you thought you could definitively disprove the idea that all the observable statistics of QM could be reproduced by rules that are "local" in the specific narrow sense I had described to you--remember all that stuff about having computers determining what the value of local variables at each point in spacetime should be, using only information about the value of local variables in the past light cone of that point, plus the general rules programmed into them (which take that information about the past light cone as input, and spit out the value of local variables at that point as output)? This is a narrow and mathematically well-defined question (and is based specifically on how Bell defined 'locality'), it's completely irrelevant to the question whether or not the *idea* for the rules that I programmed into the computers that perform these local calculations came from looking at some equations that are written in a 'non-local' way (i.e., the equations generate their predictions by evolving a single 'state vector' for the entire spatially-distributed system). Do you understand this distinction between the narrow, well-defined definition of "local rules" (if you're unclear on what I mean here, please ask), and broader questions about what inspired the rules themselves? And are you claiming that even if we restrict our attention to the narrow definition of "local rules", you can still say with 100% certainty that no such "local rules" can accurately reproduce all the predictions about measurement outcomes made by QM? Your question, as outlined above, is completely devoid of interest to me as a physicist. I am interested in physical models that give an insight into how things come about. And yes, I am 100% certain that local rules, with local models for deciding what statistics should be reproduced to mimic quantum results on entangled systems, are impossible. And are you 100% certain of that last statement even if we define "local rules" in the specific narrow sense I have described? Your comment that my question concerning this narrow definition of locality is 'devoid of interest' to you makes it unclear whether you were actually willing to stick to the narrow definition in addressing my question, as I had requested. It is of no interest. You, and Rubin, advertised your work as a local explanation of the EPR statistics. On detailed examination and pressing, you admit that this is not the case: you simply take the quantum results and build some Rubin Goldberg machine that will reproduce those statistics. So what? My urn model is simpler and does the same thing. The thing that bothers me is that I have spent so much time arguing this when, in the final analysis, you do not have a local account of the EPR results. All your machinery is of no use, since any account of EPR must fit in with the rest of quantum mechanics -- it is not something you can simply abstract away and treat in isolation. The cos^2(theta/2) comes from applying the strict rules of quantum mechanics to this entangled state -- it is not an arbitrary formula dreamed up simply to account for some observed statistics. The fact that experiment followed this distribution was a profound surprise to many -- that is why locality and non-locality are such contentious issues. The cos^2(theta/2) works also for 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+> Richard Feynman was frequently a bit "over the top" in his popular accounts of physics. He is unkind to Newton, since the 1/r^2 form of the law of gravitation follows simply from spherical symmetry and conservation of flux. Coulomb's law can be derived in much the same way. The mathematical basis is Gauss's law. So generate whatever models you like, but it is disingenuous to claim that you are giving a local explanation for the EPR correlations. It is not local, because the end situation is not local, but the infinitely many Alice and Bob do recover the right statistics in each of their branches, just by the correlation made locally when they prepare their state. Action at a distance is not needed, *because* the state 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+> describes an infinity of relative states. Bell concludes to action at a distance because he discards the superposition after the measurement. Bruno Bruce To try to restate this "specific narrow sense" one more time, note that at th
Re: Non-locality and MWI
On 27 Apr 2016, at 06:49, Bruce Kellett wrote: On 27/04/2016 1:51 pm, Brent Meeker wrote: On 4/26/2016 8:38 PM, Jesse Mazer wrote: OK, let's say experimenter A measures particle 1, and experimenter B measures particle 2. Any given copy of particle 1 has a "label" that says something about the state of 2--we can imagine that the copy of particle 1 carries a little clipboard on which is written down both its own quantum state, and a quantum state it assigns to particle 2. When that copy of 1 is measured, it not only adjusts its own state (to an eigenstate of the measurement operator), it also adjusts the state it has written down for 2. You seem to be assuming, in effect, that when a copy of 1 adjusts what it has written down for the state of 2 on its own clipboard, this must mean that copies of 2 also instantaneously adjust what they have written down about *their* own state. However, in a copying-with- matching scheme, there's no reason this need be the case! That's pretty much the many-universes model that Bruno proposes. But it's non-local in the sense that the "matching scheme" must take account of which measurements are compatible, i.e. it "knows" the results even while they are spacelike separated. Exactly, the model assumes the results it is trying to get. It is not a local physical model because the statistics do not originate locally. The statistic did originate locally. Alice and Bob did prepare the singlet state locally, and then travel away. They are in infinitely many worlds, and in each with opposite spin. The cos^2(theta) is given by the math of the 1/sqrt(2)AB(I+>I-> - I->I+>)) = 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+>. With your explanation to Jesse, I keep the feeling that you talk like if Alice or Bob reduce the wave after their measurement, but they just localize themselves in the relative branches. Like Jesse said: no "matching" between copies of measurement- outcomes at different locations takes place at any location in space- time that doesn't lie in the future light cone of both measurements. Only if a reduction of the wave occur would a genuine action at a distance have to take place to keep up the cos^2(theta). In the MWI, we keep it intact because 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+> describes a global state of the multiverse. There is a form on non separability, but it does not use non local action. It uses only the fact that the many Alice and Bob are in the same branches and remains in the same branches when travelling away of each other in each branch, but they both cannot know in which branch they are, and what is the spin of their respective particles. They do know that they are correlated by 1/sqrt(2)ABI+>I-> - 1/sqrt(2)ABI->I+>, but that is all they can know. Bruno Bruce -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout. http://iridia.ulb.ac.be/~marchal/ -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.