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] > <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>. > > > > > 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 [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.
