> On 12 Jul 2018, at 14:09, Bruce Kellett <[email protected]> wrote: > > From: Bruno Marchal <[email protected] <mailto:[email protected]> >>> On 12 Jul 2018, at 04:04, Bruce Kellett <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> There are no up' or down' branches. >> >> >> ? (That contradicts directly what you just said). A up-branch is just a >> branch where Alice saw or would see “up”. > > You were the one who introduce up-prime and down-prime branches. I maintain > that there are only two branches on each and every measurement, an up-branch > and a down-branch.
In which direction? > > ...... >>> Each measurement splits a branch, but branches never meet or recombine. >> >> Because they both measure in the same direction (not sure how they do that >> btw), but for Bell’s inequality, some measurement are not “orthogonal”. >> Partial fusion is in play, which forbids ti associate each personal >> experience with any definite Alice (Bob) in the branching. > > Perhaps I was not sufficiently clear. I am considering a series of N trials > in which both Alice and Bob independently choose random magnet orientations. > So if the relative angle is theta, the probabilities for combined results are: > > Alice gets up: then Bob has probability sin^2(theta/2) for up, and > probability cos^2(theta/2) for down. > > Alice gets down: then Bob has probability cos^2(theta/2) for up, and > probability sin^2(theta/2) for down. > > If theta = 0, then if Alice gets up then Bob down 100%.; Alice down then Bob > up 100%. > If theta = 120 degrees, then if Alice gets up, then Bob gets up 75% > probability, and down 25% probability. > And so on for other angles and combined results. It is these probabilities > that are crucial for getting the correct correlations when Alice and Bob meet. > > Now if you can get these correlations without the non-local knowledge of this > relative angle, then you have a local explanation. But you will never be able > to produce such a set of probabilities locally -- the relative angles are set > at random: non-locally at space-like separations. But the result of the measurement are determined by the singlet state. They just cannot known there local angles. When they measure in non orthogonal “direction”, the probabilities depends, for all Alice-Bod couples, of that state, which is unknown to both of them.I am OK that it is non-local, but that does not entail that when Alice makes a measurement, she influence Bob’s outcome by a FTL influence. They just get aware locally of which sub partition they both belong. > > > >>> So the Alice that meets a Bob over coffee after the N trials is the Alice >>> with one particular branching history. >> >> Again, this begins to be too much ambiguous, if not non sensical for me. > > This is the heart of the matter. If you don't understand this, then you don't > understand how the correlations are formed. >From entanglement. > >>> The Bob she meets is necessarily in the same world, >> >> At the moment of the meeting, yes. But that is a far cry to say that it is >> the “physical Bob” she started with, in the case of "non orthogonal >> measurements”. But OK, for this scenario. > > We assume randomly non-orthogonal measurements. And neither Alice nor Bob can > switch between branches, ? They don’t know which branches they are in, right at the start. That is equivalent to belonging to many threads at once. Only later will they get more precision on this. The singlet state explains why they will observe the correlations when coming back together, without having to have any FTL. Once a superposition exist, it never disappear, and the correlations just reflect the type of interaction they did have to prepare the singlet state. > so the Bob that Alice meets has a set of measurement made all in this same > world -- the world in which Alice has made her measurements. But there is an infinity of such world, where Alice find any possible results. Same for Bob. The results are correlated, because they are in the right corresponding relations, in all of them. My feeling is that you introduce some collapse somewhere. > In fact, the multi-branching tree forms a giant superposition, and we have > just singled out one component of this superposition. There is nothing at all > mysterious in this -- it is what physicists do all the time when they perform > calculations in momentum space -- on just one component of the superposition > that makes up a wave packet. That makes sense. > > >>> and he has a similar particular branching history corresponding to just >>> one world. There are 2^N such meetings, each with unique branching >>> histories. The wonder of the singlet state is that for all these Alice/Bob >>> meetings, comparison of the data recorded in their lab books always gives >>> correlations that agree with quantum theory and violate the Bell >>> inequalities. >> >> To get them, they need non orthogonal measurement, with different >> probabilities (cos^2(some angle)), and your identity relations does no more >> work. > > We have assumed non-orthogonal measurements, ones with the relative angles > set randomly at spacelike separation, ie., non-locally. No problem with this. Still not see why we would need single branch physical FTL when we look at the “giant superposition”. I don’t see at all why and how any FTL would be needed once we agree that both the evolution and the tensor product are linear. I see only local interaction, shared by people belonging to the (infinitely many) corresponding states described by the singlet state. 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 [email protected] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/everything-list > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- 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.
