On Mon, Aug 19, 2019 at 6:41 PM Bruno Marchal <marc...@ulb.ac.be> wrote:
> On 19 Aug 2019, at 04:02, Bruce Kellett <bhkellet...@gmail.com> wrote: > > On Sat, Aug 17, 2019 at 11:00 PM Bruno Marchal <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. 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. 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. You are the one who is required to provide a local explanation. You claim that it is a consequence of many worlds, or the absence of collapse. OK, then convince me....... > 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 can offer you considerable odds that you will not be able to do this. 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 view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLQw1a3AP-nsUP3n_7EPH%2BPWxKEV7vZqv%3D5S3fnKxK4zow%40mail.gmail.com.
