On Friday, April 20, 2018 at 12:30:00 AM UTC, smitra wrote: > > On 20-04-2018 01:38, [email protected] <javascript:> wrote: > > On Thursday, April 19, 2018 at 10:11:38 PM UTC, smitra wrote: > > > >> On 19-04-2018 22:52, [email protected] 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 > > One can a priori rule out any non-local effects using the fact that the > dynamics as described by the Schrödinger equation is local. So, in any > theory where there is no collapse and everything follows from only the > Schrödinger equation, there cannot be non-local effects other than due > to common cause effects. Then suppose that in an example where things > are simplified to allow for Alice and Bob thought experiments to be > discussed without having to rigorously show how Alice, Bob and the > experimental apparatus used are to be extracted from the wavefunction > one does see non-local effects, then it follows that these non-local > effects are artifacts of these simplifications. Now, in standard quantum > mechanics one does routinely make such simplifying assumptions, this > allows for QM to be useful as a practical theory, but we then also know > that strictly speaking, it's not how Nature really works. > > Saibal >
*Maybe Bruce can evaluate your comments, but for me I don't see how collapse or not, SWE or not, has anything to do with Bell statistics. We get these correlations that imply non locality in this universe or in any other. What am I missing? 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.
