> On 19 Aug 2019, at 13:59, Bruce Kellett <bhkellet...@gmail.com> wrote: > > On Mon, Aug 19, 2019 at 6:41 PM Bruno Marchal <marc...@ulb.ac.be > <mailto:marc...@ulb.ac.be>> wrote: > On 19 Aug 2019, at 04:02, Bruce Kellett <bhkellet...@gmail.com > <mailto:bhkellet...@gmail.com>> wrote: >> On Sat, Aug 17, 2019 at 11:00 PM Bruno Marchal <marc...@ulb.ac.be >> <mailto:marc...@ulb.ac.be>> wrote: >> >> The state is ud - du, for d = down and u = up, with the usual sqrt(2) = 1. >> >> The idea is that when Alice see her photon being u, she knows that whatever >> she will be interact with will be consistent wit her photon being u and with >> bob photon being d, including the bob she could ever manifest herself >> relatively. >> >> That is exactly the magic that needs to be explained. > > I don’t see this. ud - du predicts this, by the quantum formalism. > > Yes, and that formalism requires what for you is "the dreaded collapse". > Think about it. How else does this work in conventional QM? > > >> The magic comes only from the idea that there is one Alice and one Bob, >> which would make this reasoning obviously invalid, or introduce faster than >> light physical influence. >> >> The argument does not depend on any "one world" assumption. The problem is >> clearly present even in the Everettian setting, when there are copies of >> Alice and Bob who see each result. These always exist, since both up and >> down results are always possible for any measurement on the separated >> singlet particles. > > I don’t see this. Alice and Bob have prepared the particle together (or by > some entanglement swapping technic), the state ud-du require the > correlations, in all base. Once separated, they can only access to their > correlate parts, which requires the “creation” of “new” Bob and Alice. > > No, this is just an appeal to magic. "They can only have access to their > correlate parts"? That is what you have to explain. What prevents them from > accessing all the other combinations.
Unitarity. > > Look, it is actually quite simple for you. All you have to do is provide a > local causal explanation for the appearance of the cos^2(theta/2) dependence > on the relative angle between Alice's and Bob's separate and independent > measurements. If Alice gets 'up', Bob has a probability of sin^2(theta/2) of > getting 'up', and cos^2(theta/2) probability of getting 'down'. Do that, and > I might be convinced. So far, you haven't even come close. The local causal explanation, here, is the wave equation. The non-locality (the violation of Bell’s inequality, or GHZ’s even more weird happening) is explained by the causal evolution of the wave in a higher dimensional space. Everett has been criticised for giving the same prediction, but that was the idea: showing that the average relative observer in the relatives state theory gives the same prediction than conventional QM. There is no need to assume an Heisenberg cut or a von Neuman-Wigner ultimate first person reduction of the wave: there is just no collapse, and observation/measurement is self-entanglement. > > > It is up to you, if you think that some FTL influence occur, to explain why > and how. > > It is not up to me to provide a local explanation. I claim that the effect is > non-local. But both Digital mechanism and Quantum mechanics suggests, if not impose some “non-locality”. My point is that with the relative state notion, that you get when you decide to apply QM on the couple observer + observed, the non-locality, the inseparability of D’Espagnat, is a true observable phenomenon, but it does not requires faster than light influence: it is a statistical effect depending on our indetermination on which histories we belong too in the infinities of histoires described by the singlet state. > You are the one who is required to provide a local explanation. H phi = E phi If you can show how this implies FTL action at distance, you might try to show me. > You claim that it is a consequence of many worlds, or the absence of > collapse. OK, then convince me……. You are the guy making the extraordinary claim, which in my opinion contradicts already special relativity (or pushing the instrumentalist “shut up and compute” maximally). The singlet state is independent of the base in which it is written. It is a state where both Alice and Bob could find any result, then you have to take into account that Alice share the world with Bob, but they have different indetermination in between the measurement. Your four worlds interpretation get wrong when you take all the relative state into account. I prove this to myself by a simple induction on the lattice defining a localised object, then all interactions generates a wave of self-entanglement with the environment at each step of the histories. In this way, despite everything is described by a local/causal history, it will look indeterminate and non local from some classes of histories. The astract treatment of this is well done in the book on Quantum Computation by Hirvensalo. If you see FTL in the quantum non-locality, or in Aspect experience, I would advise you attempt to change your interpretation of the formalism. > > > Both EPR and Bell assumes that "Alice and Bob” are well defined and keep > their identity throughout the experience, which indeed would require some FTL > influence, but I don’t see that FTL when we keep all branch of the > superposition into account. > > Bell does not require that assumption. I have given you full accounts of Bell > that did not rely on any collapse assumption, accounts in which both Alice > and Bob get both up and down results. You just have to show how the (theta/2) > dependence between their results arises from purely local interactions in the > many worlds situation. I did, with special different theta, and it is not much different than in some links we gave, but you attribute a constant identity to Alice and Bob which did not make sense. The theta/2 dependence is what requires to interpret the singlet state by a state of infinitely may “universes” in which Alice and Bob have all state possible, but with the correlation. When Alice make a measurement, she knows which Bob she will meet. If Bob makes a measurement he will know which Alice he will meet, but relatively to their states. That makes things highly non-local from the perspective of all persons able to interact, but without any “real physical influence at a distance”. It is a place where Leonard Susskind is a bit too quick, when he says (on YouTube but also in his book that I have cited) that we cannot simulate the quantum non locality with a computer “in real time”. Of course he is correct, but if you simulate the schroedinger equation of the couple Alice and Bob doing all sorts of experiments, you will be obliged to get all the superposition but in fine, in the majority of histories, the Alices and the Bobs will measure and infer the right cos(theta/2). The difficulty is that “you” have to sample the answers of many Alices and Bob. > > I can offer you considerable odds that you will not be able to do this. If you can get FTL action at a distance from QM, I will automatically think that you take some aspect of your interpretation too seriously or naively. I might be wrong, but most argument claiming there exists, by EPR-Bell-Aspect either use some implicit collapse somewhere, or take the notion of worlds in a sense which eludes me. I will give more thought on this, some quantum thought experience might perhaps change my mind, but I doubt the singlet state will be enough. We might discuss the GHZ state, as it does no more involve probability, and is even more strange. You might try to use it to show the existence of FTL. 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 > <mailto:everything-list+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/everything-list/CAFxXSLQw1a3AP-nsUP3n_7EPH%2BPWxKEV7vZqv%3D5S3fnKxK4zow%40mail.gmail.com > > <https://groups.google.com/d/msgid/everything-list/CAFxXSLQw1a3AP-nsUP3n_7EPH%2BPWxKEV7vZqv%3D5S3fnKxK4zow%40mail.gmail.com?utm_medium=email&utm_source=footer>. -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/6AFD4FFF-8AD6-4CB5-BC1E-A89A1199BE8E%40ulb.ac.be.
