On Thursday, April 19, 2018 at 10:11:38 PM UTC, smitra wrote: > > On 19-04-2018 22:52, [email protected] <javascript:> wrote: > > On Thursday, April 19, 2018 at 2:42:37 PM UTC, Bruno Marchal wrote: > > > >> On 18 Apr 2018, at 15:45, Bruce Kellett <[email protected]> > >> wrote: > >> > >> From: BRUNO MARCHAL <[email protected]> > >> > >> On 17 Apr 2018, at 13:52, Bruce Kellett <[email protected]> > >> wrote > >> > >> But note particularly that the spin measurement is made in the > >> basis chosen by the experimenter (by orienting his/her magnet). > >> > >> OK. > >> > >> The outcome of the measurement is + or -, > >> > >> For Alice and Bob, OK. > >> > >> not one of the possible infinite set of possible basis vector > >> orientations. The orientation is not measured, it is chose by the > >> experimenter. So that is one potential source of an infinite set of > >> worlds eliminated right away. The singlet is a superposition of two > >> states, + and -: it is not a superposition of possible basis > >> vectors. > >> > >> ? (That is far too ambiguous). > > > > ????? It is not in the least ambiguous. The singlet state is not a > > superposition of basis vectors. > > > > ? > > > > The singlet state is the superposition of Iup>IMinus> and (Minus>Iup>. > > > >> If you think about it for a little, the formalism of QM does not > >> allow the state to be written in any way that could suggest that. > >> > >> I don't know what Everett says in his long text, but if it is any > >> different from the above, then it is not standard quantum mechanics. > >> Deutsch is a different case. He has a very strange notion about what > >> constitutes different worlds in QM. Standard QM and Everett's > >> interpretation are very clear: different worlds arise by the process > >> of decoherence which diagonalizes the density matrix. The net effect > >> is that worlds are, by definition, non interacting (contra Deutsch's > >> ideas). > >> > >> ? > > > > This relates to your lack of comprehension above. > > > > Patronising !!!!!!! > > > >> Deutsch has two distinct notions of "world" in his approach. He has > >> the standard Everettian notion of a "relative state" corresponding > >> to each term in the superposition of possible measurement outcomes. > >> These relative states are made definite by decoherence, > > > > Relatively. Decoherence is only entanglement (with NON-collapse). > > > >> and then correspond to different, effectively orthogonal, worlds, > >> each of which represents the experimenter observing one particular > >> result. But Deutsch also has the idea that the infinity of possible > >> bases for an unpolarized qubit also represents an infinity of > >> worlds. > > > > That is necessary, and Everett explains this well when he shows that > > the choice of the base to describe the universal wave is irrelevant. > > > > (A bit like the choice of the universal Turing formalism is irrelevant > > to get the theology and the physics). > > > >> This is quite a different notion, and does not occur in Everettian > >> theory. > > > > I disagree with this. > > > >> In this second notion of "world", the worlds remain in > >> superposition and continue to interfere -- there is no separation > >> into disjoint, non-interacting worlds. In fact, it is precisely this > >> continued interference of these supposed "worlds" that is the > >> explanation for the action of quantum computers -- which Deutsch > >> seems to think actually *prove* his notion of quantum "many-worlds". > >> He is out on a limb on this one, and few experts, even in the > >> quantum computing field, agree with Deutsch on this new notion of > >> "worlds". The essential continued interference between the different > >> basis states in fact means that the "worlds" remain inextricable > >> "one world". (See some of Scott Aaronson's comments on Deutsch and > >> many-worlds in his lecture notes on quantum computing.) > >> > >> So when you continue to refer to an "infinity of worlds" for the > >> measurements on the entangled spin states, you are using a notion of > >> "world" that does not occur in Everett, and is inherently > >> controversial, if not entirely meaningless. > > > > I use the “Herbrand” interpretation of quantum mechanics without > > collapse. I mean: it is literal QM (in a sense that logicians have > > made precise) without collapse up to a choice of any arbitrary base. > > I don’t believe in any worlds, to be clear. It always means some > > reality satisfying some formal constraints. > > > >> But even if you can manufacture an infinity of universes, you still > >> have not shown how this removes the non-locality inherent in the > >> quantum formalism. > >> > >> You have not shown non locality. > > > > I have demonstrated non-locality in the Everettian context many > > times. The simplest demonstration was in the timelike separation of > > Alice and Bob's measurements. It is in the archives if you don't > > recall the details. The argument then is that any local influence that > > would explain the timelike separated measurements must also work for > > spacelike separated measurements, and that is not possible. > > > > At all time there is an infinity of “worlds”. When Alice chose her > > direction, that remains true, and her measurement will tell us if she > > belongs to a world with “spin” down or up, she will automatically > > know that whatever Bob she will meet, will have the corresponding > > results, no action at a distance here. > > Again, you keep referring to this non-existent infinity of worlds — > > > > > > “worlds” would be better. > > > >> a notion that has nothing to do with Everett or his interpretation > >> of quantum theory. "... She will automatically know that whatever > >> Bob she will meet, will have the corresponding results...". This is > >> precisely the question that you have not answered -- how does this > >> happen? > > > > Because in ALL “worlds” Alice and Bob have they spin described by > > the no-separable singlet state. The statistics seems non-local, due to > > their ignorance of which partition of the wave function they belong > > to. > > > > But that would be the same for all worlds; statistics which imply > > instantaneous action at a distance. You haven't removed non-locality, > > but in fact extended it to many worlds, and then you must ignore the > > elephant in the room; the absurdity of postulating the many observers > > with identical memories, histories, etc. I don't see that anything has > > been gained. AG > > The non-locality is eliminated here via a common cause effect. But the > common cause explanation only works if you don't get rid of the > superposition that includes sectors where Alice and Bob find different > results. > > Saibal >
Sorry. I don't follow your comments. Bruno claimed the statistics in all worlds imply non-locality. AG -- 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.
