On Sunday, April 22, 2018 at 5:22:48 PM UTC, agrays...@gmail.com wrote: > > > > On Sunday, April 22, 2018 at 4:19:44 PM UTC, Bruno Marchal wrote: >> >> >> On 20 Apr 2018, at 03:18, Bruce Kellett <bhke...@optusnet.com.au> wrote: >> >> From: Bruno Marchal <mar...@ulb.ac.be> >> >> On 18 Apr 2018, at 15:45, Bruce Kellett <bhke...@optusnet.com.au> wrote: >> >> From: Bruno Marchal <mar...@ulb.ac.be> >> >> On 17 Apr 2018, at 13:52, Bruce Kellett <bhke...@optusnet.com.au> 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? >> >> >> >> 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 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. >> > > *Bruno, please get a clue. In Bell experiments Alice and Bob are NOT > space-separated. They are in the same laboratory! It's from the correlation > results that action at a space-separated "influences" is INFERRED. It was > Bell's theorem that allowed such experiments to be done, since prior to > that, and presently, and forever, it's IMPOSSIBLE in principle to > space-separate Alice and Bob, and do measurements on both. AG* >
*Correction to above text:* *Bruno, please get a clue. In Bell experiments Alice and Bob are NOT space-separated. They are in the same laboratory! It's from the correlation results that "action" (aka "influences") for space-separated events is INFERRED. It was Bell's theorem that allowed such experiments to be done, since prior to that, presently, and presumably forever, it's IMPOSSIBLE in principle to space-separate Alice and Bob and do measurements on both. AG* > > >> I am not even sure we can define what could be an action at a distance in >> the quantum formalism. >> > > > *It means, for the singlet state, that conservation of spin angular > momentum is conserved for space-separated events. Not saying I believe it, > but that's what it MEANS. AG* > > >> 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, >> >> *To believe there are additional Alice's and Bob's is ridiculous on its >> face. Admit it! AG* >> >> > 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 everything-li...@googlegroups.com. >> To post to this group, send email to everyth...@googlegroups.com. >> 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.
