On Wed, Dec 22, 2021 at 10:12 PM smitra <[email protected]> wrote: > On 21-12-2021 22:48, Bruce Kellett wrote: > > > > In general, that is not true. When both Alice and Bob set their > > polarizers randomly while the particles are in flight, the fact that > > Alice might get |up> tells her nothing about what Bob will get at some > > randomly different polarizer orientation. You seem to be stuck with > > thinking in terms of parallel polarizer orientations. > > It's not true only when the polarizers are orthogonal. Whenever the > polarizers are not orthogonal, Alice will gain some amount of > information about what Bob will find given the result of her > measurement. For Bob, the probability of finding up or down are always > 1/2, but after Alice makes her measurement, the conditional probability > of what Bob will find, given her measurement result will not be equal to > 1/2 for both outcomes if her polarizer was not orthogonal to that of > Bob, so Alice will have gained information about Bob's measurement > result. >
The conditional probability you refer to is defined only non-locally. >> In the MWI > >> there is no such mysterious gain of information due to the correlation > >> being caused by common cause when the entangled pair is created > > > > Rubbish. If there were a common cause, then that would have to depend > > on the final polarizer orientations. And those are not known at the > > time of creation of the entangled pair. You are, then, back with some > > non-local influence (or retro-causation). > > The setting of the polarizers will be the result of some physical > process. Whatever you specify for that process should be included in the > analysis of the problem. But when you do so, it's inevitable that in an > MWI analysis, there is not going to be any nonlocal effect other than > trivial common cause effects. > I see. So in desperation you resort to the superdeterminism escape. MWI is not necessary for the understanding of the correlations of entangled particles, as my simple example shows. In an actual experiment, the analysis is identical in many-worlds and collapse models. The additional worlds in MWI add nothing to the explanation. They are, therefore, otiose, and MWI can be discarded. 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/CAFxXSLQ5oroH0Gn9HemqBh_310s6zvDjsz81d%2BSGkt0Teq_biA%40mail.gmail.com.
