On Mon, Jun 18, 2018 at 7:38 AM, Bruce Kellett <[email protected]> wrote:
> From: Jason Resch < <[email protected]>[email protected]> > > > On Sun, Jun 17, 2018 at 6:24 PM, Bruce Kellett < > <[email protected]>[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. > Is it ever full/complete? Isn't Decoherence only ever approximate? > 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. > > You get unitarity when you couple Decoherence with many worlds. No world destroying magic is required to cause other universes to go to zero, and our (how lucky we are) world to go to 1. 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 was used in Bohemian mechanics, and later by Everett. See "'7. THE ORIGIN OF THE STATISTICAL ENSEMBLE IN THE QUANTUM THEORY" of: http://cqi.inf.usi.ch/qic/bohm2.pdf > > > 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-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! > > This is what David Deutsch was referring to when he says he has yet to receive a plausible reply. I think the answer is, however, rather clear if you only consider the wave function and its superpositions as a concrete and physically existing object. > 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? > > It's superpositions, and the exponential number of them it could simultaneously possess. Would the AI have just a single experience, or many, perhaps trillions, or 10^100 of them? > > [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-principle.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? > Let's make it more concrete and say there are only 360 possible polarizations, each having an equal probability. The photon pair is then in a superposition of 360 possible states. The photon pair must be considered as a single object, because if your photon is 240 degrees, mine is -240 (120 degrees), and so on. There are only 360 possible values that could be obtained from measurement, not (360 * 360). When I measure my photon on Pluto, I am self-locating myself to a branch (one of 360 possible branches of the wave function corresponding to each of the 360 possible polarization of the photon on Pluto). Once I have located myself to this branch, I may not know which measurement angle you will set your filter at, I remain in a super position of all possible measurement angles you might choose (let's say there are 3 possible measurement angles). After your measurement, you first transmit, not your result, but your measurement angle. Once the photons from this radio signal reach me, I have located myself to one of the 3 possibilities for the measurement angle. At this moment, I have all the information I need to be able to completely predict the statistics of your measurement result, based on my measurement result and angle which I knew since the time of measurement, and now with your measurement angle information having reached me. When you transmit your measurement result to me, I find it in agreement with my expectations for having located myself to a branch that had (360 * 3) possibilities that were unknown to me at the time prior to performing the experiment. > > 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. > > Can you point out the error in my example above (with added clarifications)? > > >> Regarding preferred bases, both of the papers I provided which began this >> thread address that question: >> >> 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 >> >>> *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. > > Let me put it another way, why is the preferred basis problem not a problem for QM generally? Collapse/Single Universe theories have a number of (in my view) fatal flaws. The only arguments I see leveled at MWI is that (hey, there there are still come things left to figure out). But these things are problems for QM generally, not MWI. Such as preferred basis, Born rule, etc. 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. > I see. I thought you were arguing against MWI being true. I am fine with the bullet dodger view. It's always best to remain agnostic and try to disprove as many theories as we can. Jason -- 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]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
