On Thursday, April 19, 2018 at 2:42:37 PM UTC, Bruno Marchal wrote: > > > On 18 Apr 2018, at 15:45, Bruce Kellett <bhke...@optusnet.com.au > <javascript:>> wrote: > > From: Bruno Marchal <mar...@ulb.ac.be <javascript:>> > > On 17 Apr 2018, at 13:52, Bruce Kellett < <javascript:> > bhke...@optusnet.com.au <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>. > > > > > 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 * > What is the particular magic that you put in the mix to ensure that the > correct correlations emerge? > > > Only QM, without collapse. > > > > > If there is an infinity of worlds, there must be an awful lot of selection > going on -- superfluous worlds surreptitiously eliminated.... > > > In QM without collapse, a superposition NEVER disappears. It only seems so > from the first person perspective of the observers. > > Looking to a Shroedinger cat *is* conceptually equivalent with a > duplication Helsinki-Washington + Helsinki-Moscow. The first person cannot > feel the split, like Everett explained for the superposition. > > > > > See Maudlin for a fuller account of the absurdity of this notion. > > > In the Everett, the locality is preserved by the fact that you need > interaction/measurement at some point, and the superstition get > “contagious” only at the speed of light, something zurek explained well in > his account of decoherence. > > > This is what you suggested above -- your view is that locality is > maintained by refusing to accept the possibility of non-locality. Sorry, > but that does not wash, scientifically or logically. > > > That reasoning is the same as creationist. Your theory of evolution > assumes that God has not made the world in six days, so, there is no doubt > that you can only see confirmation of it. Of course that is not valid here, > nor above. > > > That is your reasoning, not mine. > > > Just read what you have written above. > > > 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 everything-li...@googlegroups.com <javascript:>. > To post to this group, send email to everyth...@googlegroups.com > <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 everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
