On Sunday, April 22, 2018 at 4:19:44 PM UTC, Bruno Marchal wrote: > > > On 20 Apr 2018, at 03:18, Bruce Kellett <[email protected] > <javascript:>> wrote: > > From: Bruno Marchal <[email protected] <javascript:>> > > On 18 Apr 2018, at 15:45, Bruce Kellett < <javascript:> > [email protected] <javascript:>> wrote: > > From: Bruno Marchal <[email protected] <javascript:>> > > On 17 Apr 2018, at 13:52, Bruce Kellett < <javascript:> > [email protected] <javascript:>> 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>. > > > Those are not generalized basis vectors: they are eigenfunctions of the > spin projection operator in a particular basis. The singlet state is not a > superposition of vectors from different bases. > > > Did I say that? >
*You wrote |minus> when you meant |dn>, thus confusing the issue of bases. AG * > > > > 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 !!!!!!! > > > Merely pointing out your apparent lack of comprehension when you fail to > appreciate the difference between the eigenvectors of a particular operator > and the free choice of a basis for Hilbert space. > > > You aggravante your case. > > > > 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). > > > So what? > > 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. > > > Sure, the choice of basis is irrelevant. It is just that some bases are > more useful than others. And there is no use at all in trying to use all > bases at once! > > (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. > > > Well, you are wrong. > > 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. > > > I think you believe in a world. How else do you go about your daily life? > > > Like in a dream. Like in any computations which get a high relative > probability. Of course you can call that worlds, but they have no > fundamental ontology. But please read my papers, or the old posts. > > > > Or are you like most mathematicians: believing in platonism at work, but > believing in nominalism the rest of the time? > > > I am a scientist. I keep my belief for myself except those I put on the > table as hypotheses, and reason from that. I do that in theology, which is > not done frequently especially since 1500 years (but some have the right > spirit, like Spinoza, and many others less well known). > > > > > 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. > > > No, due to the fact that any any "world" in which they find themselves the > correlations indicate non-locality. > > > Yes, but not any action at a distance. > *What is the content of non locality if not action at a distance, particularly for space-like separated events? AG * > > > > > What is the particular magic that you put in the mix to ensure that the > correct correlations emerge? > > > Only QM, without collapse. > > > That is truly magical, and you have no evidence for this whatsoever. > > > It follows from both QM and Comp. If Alice and Bob are space-separated, I > cannot even makes sense of how you can measure correlations, given that > once they are separated, whatever result they got, will be shared with > different Alice and Bob in different branch. I am not even sure we can > define what could be an action at a distance in the quantum formalism. The > notion does not even makes sense when we assume special relativity. The > only reason to believe this is the habit to think that there is only one > bob and one Alice, which makes no sense once separated, unless they are > correlated with a third observer, but then, again by looking at the wave > without collapse, there will be no action at a distance. The no locality is > only an appearance due to the fact that we belong to infinities of > histories, and cannot known which one we are in. > > 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] <javascript:>. > To post to this group, send email to [email protected] > <javascript:>. > Visit this group at https://groups.google.com/group/everything-list. > For more options, visit 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.
