> On 18 Jun 2018, at 14:38, Bruce Kellett <[email protected]> wrote: > > From: Jason Resch < <mailto:[email protected]>[email protected] > <mailto:[email protected]>> >> >> On Sun, Jun 17, 2018 at 6:24 PM, Bruce Kellett < >> <mailto:[email protected]>[email protected] >> <mailto:[email protected]>> wrote: >> >> Maybe it just means that we don't yet fully understand the collapse. There >> are plenty of possibilities that don't resort to magic. >> >> >> I agree. >> >> But what facts about our observations of collapse are not already fully >> explained by Decoherence? > > Decoherence does not explain the transition from FAPP orthogonality to full > orthogonality of the branch states. In other words, decoherence is unitary, > so cannot explain the non-unitary trace over unobserved environmental > entanglements inherent in the projection of actual experimental results. > >> In other words, what is left to solve about it? I thought Decoherence solved >> this (back in 1952 with Bohm). > > Decoherence was not introduced by Bohm. The idea originated with Dieter Zeh > in around 1974, if I remember correctly.
It seems to me that decoherence is already in Everett (1957). But the word is used in different sense by different people. Bruno > >>> When you say non-local what type of non-locality do you mean? It is a >>> local theory in the sense that physical objects interact only with other >>> physical objects in their proximity, and carry information only at luminal >>> or subluminal speeds. See Q12 on >>> <http://www.anthropic/>http://www.anthropic >>> <http://www.anthropic/>-principle.com/preprints/ >>> <http://principle.com/preprints/>manyworlds.html >> >> Price's argument here has been shown to be invalid -- he surreptitiously >> relies on non-locality. >> >> >> Care to explain this non-locality and where it appears in a MWI explanation >> of the EPR paradox, for example? I've provided explanations on this list >> before of how EPR/Bell operates under MWI without FTL influences. So if you >> think they are required I would be interested to know where you think they >> appear and are necessary. > > I have pointed out the flaw in Price's account previously on the list. Tipler > makes the same mistake, as do several others. But rather that going through > the argument here, I will postpone it to my discussion of your attempted > local account. You make essentially the same mistake, so we can look at it > then. > >> John Clark often says MWI is non local because the branches are not local to >> each other, but I think this is a redefinition of the common sense use of >> the term locality in physics. Is this what you mean by MWI being non local? > > Not really, but John does have a point. > >> How do you explain the finite computational resources of a table-top >> quantum computer factoring a prime number in seconds when it would take a >> classical computer the size of the solar system 10^100 years to do the same >> calculation? >> >> David Deutsch notes that quantum computers present a strong challenge to >> defenders of single-universe interpretations, saying “When a quantum >> computer delivers the output of such a computation, we shall know that those >> intermediate results must have been computed somewhere, because they were >> needed to produce the right answer. So I issue this challenge to those who >> still cling to a single-universe world view: if the universe we see around >> us is all there is, where are quantum computations performed? I have yet to >> receive a plausible reply.” >> >> That might be Deutsch's opinion, but plenty of others think differently. >> Quantum computers can easily be understood in a single world account. >> >> >> But it can't be explained in non-realist views of the wave function. For >> example, those that say it is nothing but a convenient tool for computing >> probabilities. > > Why can't that account for quantum computing? > >> The reason is, here this "convenient tool" is computing results for us that >> we have no hope of ever computing ourselves. How is something which isn't >> real, and isn't really there, yielding results of computations? > > Quantum mechanics is weird! > >> You say others think differently, but don't allude to who those other >> thinkers are or what their thoughts are. Do you have an explanation for >> quantum computers that works with the assumption the wave function is not >> real? > > Yes. The particular person I was thinking of here is Scott Aaronson. He is no > fan of Deutsh's approach to quantum computing and many worlds. He points out > that quantum computers rely on interference between the components, and that > is possible only in a single world. > >> What would you say about a conscious AI implemented on a quantum computer? >> Would it or would it not be capable of existing in and experiencing "many >> simulations"? > > A quantum computer would be no different from a classical computer in so far > as implementing AI is concerned. Why would you think it would be different? > > > [snip] > >>> >>> Bell had an implicit assumption in his reasoning, which is that only a >>> single definite result is obtained by >>> all parties for any given measurement (including those not performed). >>> This is not true under MWI so Bell's reasoning that there must be >>> non-locality fails for MWI, as many-worlds lacks contra-factual >>> definiteness. >>> >>> Again from: >>> <http://www.anthropic-principle.com/preprints/manyworlds.html>http://www.anthropic-pri >>> <http://www.anthropic-pri/>nciple.com/preprints/manyworlds.html >>> >>> 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. >> >> >> As I said above, Price has an invalid argument. If Bell's theorem does not >> apply to MWI, why is it that no one has been able to give a simple, clear, >> local account of the violations of the Bell inequalities? >> >> Let me try: >> >> In the EPR experiment, a pair of photons is created. Each photon is in a >> super position of every possible polarization, and because it is created as >> a pair, it's dual in the superposed state always has exactly the opposite >> polarization (rotated 180 degrees). > > OK. > >> When you perform a measurement of your left-traveling photon on Earth, you >> become entangled (correlated) with it, and all the possible states of that >> photon, when measured, leak into the room, starting with the measuring >> device, then your eyes, then your brain, then your notebook, etc. until now >> everything is in the room, and soon Earth is now in many states which >> contagiously spread from that photon. > > OK. Your result (and you) become entangled with your environment. > >> Also, because the photon you measured was entangled (correlated) with its >> pair in the superposition, whatever result you measure for the photon's >> polarization tells you immediately what the polarization of its pair is (in >> your branch at least). So any future communication you get from me on Pluto >> will necessarily align with the result you measured. > > This is where the mistake creeps in. My measurement tells me the polarization > of the entangled photon in the branch in which my measurement was made. When > you come to measure your entangled photon on Pluto, how do you know what > branch my measurement was made in? You are at a spacelike separation from me, > and completely independent. So I ask again, how come you assume that your > measurement will be in the same branch as mine was? > > This is effectively Price's mistake, except he made it even more obvious by > writing out the equations. > >> Effectively, "single" hidden variables don't work under Bell's inequality, >> but many hidden variables do. >> >> >> Maudlin concludes his discussion of many worlds by questioning whether sense >> can be made of correlations if all outcomes occur at both ends of a >> Bell-type experiment. He concludes: "If some sense can be made of the >> existence of correlations, we have to understand how. In particular, if >> appeal is made to the wave-function to explicate the sens e in which, say, >> the "passed" outcome on the right is paired with the "absorbed" outcome on >> the left to form a single "world", then we have to recognize that this is >> not a local account of the correlations since the wave-function is not a >> local object. (Quantum Non-Locality & Relativity, 3rd Edition.) >> >> >> To see why it is local you need to trace the event back to the creation of >> the paired photons. Each photon, in a sense, has already measured each >> other. If the photons are always created in opposite aligned pairs, knowing >> one you already know the other. You know you have ended up in the branch of >> the wave function where my photon has the opposite angle of yours the moment >> you measure your photon, because both photons were created in a way that has >> such a property. > > That is what the entangled pair means. > >> Also, both of these photons, which already measured each other, traveled >> at no more than the speed of light to reach you and me. When we measured >> them, the branching of the wave function was entirely local. Starting with >> the polarization screen, then the photon detector, then the light flash, >> then your retina, the nerves along your optic nerve, then your brain. >> Nothing happened instantaneously across space or time, and nothing exceeded >> the speed of light in this process. > > Sure, the local measurements are local. But you have no local way of knowing > which branch contains my measured result. > >> >>> Regarding preferred bases, both of the papers I provided which began this >>> thread address that question: >>> >>> https://arxiv.org/pdf/1104.2324.pdf <https://arxiv.org/pdf/1104.2324.pdf> >>> Note that quantum interferences between different terms in Eq. (39) are >>> extremely small, since overlaps between macroscopically different >>> configurations, such as and , are suppressed by the huge >>> dimensionality of the corresponding Hilbert space. In fact, for any >>> observables constructed out of local operators, matrix elements between >>> macroscopically distinct states are highly suppressed, This, therefore, >>> provides preferred bases for any macroscopic systems. >>> >>> and >>> >>> https://arxiv.org/pdf/1105.3796.pdf <https://arxiv.org/pdf/1105.3796.pdf> >>> Decoherence Decoherence1 explains why observers do not experience >>> superpositions of macroscopically distinct quantum states, such as a >>> superposition of an alive and a dead cat. The key insight is that >>> macroscopic objects tend to quickly become entangled with a large number of >>> “environmental” degrees of freedom, E, such as thermal photons. In practice >>> these degrees of freedom cannot be monitored by the observer. Whenever a >>> subsystem E is not monitored, all expectation values behave as if the >>> remaining system is in a density matrix obtained by a partial trace over >>> the Hilbert space of E. The density matrix will be diagonal in a preferred >>> basis determined by the nature of the interaction with the environment >>> >>> This preferred basis is picked out by the apparatus configurations that >>> scatter the environment into orthogonal states. Because interactions are >>> usually local in space, ρSA will be diagonal with respect to a basis >>> consisting of approximate position space eigenstates. This explains why we >>> perceive apparatus states |0iA (pointer up) or |1iA (pointer down), but >>> never the equally valid basis states |±iA ≡ 2 −1/2 (|0iA±|1iA), which would >>> correspond to superpositions of different pointer positions. >> >> That is just the explanation that Schlosshauer gives. And as I have pointed >> out, it is circular. One could justify any Quantum operator at all as the >> position operator on this basis -- physics would be different. But then, >> what is required is an account of why physics is as it is. >> >> >> Could you explain to me what is the expected observational difference >> between QM and MWI, under the "preferred basis problem"? > > Why should there be a difference? MWI and CI are just alternative > interpretations -- both necessarily give the same results for any > experimental observation. But you are just avoiding the preferred basis > problem. > >> What does eliminating collapse of the wave function cause that you see as >> leading to MWI being ruled out by either any experiment or observation that >> has been performed? > > Why do you think I have said that MWI is ruled out? In Scott Aaronson's > terms, I am a "bullet-dodger": I do not stake everything on thinking that I > know the answer to everything! Since all conventional quantum experiments > give the same results under any interpretation of the QM framework, no > experiment can decide between them. Of course, unless, and until, some > collapse mechanism is actually observed. The collapse model is directly > falsifiable, and MWI would be falsified were collapse observed. Such as in > Penrose's gravitation induced collapse, or some GRW-type flash impulse > collapse mechanism. > > 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 [email protected] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/everything-list > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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