On Tue, Dec 21, 2021 at 11:53 AM Jesse Mazer <[email protected]> wrote:
> > Personally I still lean towards some version of the MWI being true mainly > because you can come up with a toy model with MWI-style splitting that > deals with Bell style experiments in a way that preserves locality but > doesn't require hidden variables (see > https://www.mdpi.com/1099-4300/21/1/87/htm ) but I see it as a sort of > work in progress rather than a complete interpretation. > I have had a chance now to look at the paper Jesse refers to here by Brassard et al. As I suspected, it is nothing more than a load of nonsense. They model the correlations in terms of what they call "non-local boxes". This is all very well, but no such boxes are physically realizable, so their argument rather loses its point. The interesting part of the paper for our discussion, is section 5, in which they give what they consider to be a local explanation of the Bell correlations. Since their non-local boxes are not physical, I will translate their argument into measurements by Alice and Bob on a pair of entangled particles in the singlet state. One can reproduce the Brassard argument by considering only the case in which Alice and Bob use parallel polarizers. The quantum correlation is then that if Alice measures 'up', Bob necessarily measures 'down'. And if Alice measures 'down', Bob necessarily measures 'up'. I continue with a quote for page 8 of the paper (translated into spin measurement terms). "For example, if Alice sees 'up', she splits, and there is a 'parallel' Alice who sees 'down'. Her system can be imagined to carry the following rule: you are allowed to interact with Bob if he saw 'down'. Should this Alice ever come into the presence of a Bob who had seen 'up', she would simply not become aware of his presence and could walk right through him without either one of them noticing anything. Of course, the other Alice, the one who had seen 'down', would be free to shake hands with that Bob." The paper goes on to elaborate this argument in terms of what happens to Bob after he splits on seeing either 'up' or 'down'. In their attempt to eliminate non-locality, Brassard et al. have been forced to resort to unvarnished magic. The split Alices and Bobs inhabit different parallel worlds, so what happens when Alice_up meets Bob is that she splits into two copies again: one who sees Bob_up and one who sees Bob_down. Similarly for Alice_down. Brassard et al. are essentially claiming that magically, the pairing of Alice_up with Bob_up can never happen. They give no rationale for this, or any physical explanation as to how this could happen. They simply claim that the pairings up-up and down-down are forbidden and can't happen -- by magic it would see. Of course this magic is local in that it happens only when Alice and Bob meet. But that is no more a physical explanation of the Bell correlations than is the existence of Brassard's "non-local boxes". Of course, the argument they give cannot be generalized to the typical case of non-parallel polarizers either. The whole paper is a crock of shit! 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]. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAFxXSLR6xGrAO3gc9hoZ1yMNrSFUT%3DByp%3D5mPOhsU%2BUHhM4%2B4g%40mail.gmail.com.
