charlylebeaugosse
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JesseM said:A) So you think that he would not have been a microscopic realist in the EPR sense? Specifically, if two entangled particles can each be measured on either of two or more noncommuting properties X and Y (like position and momentum), and measuring the value of property X for particle #1 allows us to determine with probability 1 what the value of property X would be for particle #2 if we measured property X for particle #2, then I understand the EPR paper to suggest this means there must be a local "element of reality" associated with particle #2 that predetermines the result it would give for a measurement of property X, even if we actually measure property Y for particle #2.
B) This quote by Einstein from p. 5 of Bell's paper http://cdsweb.cern.ch/record/142461/files/198009299.pdfpapers does suggest to me he favored microscopic realism in the EPR sense:
(C) Do you really think it's true that "most physicists" would prefer to relinquish locality and not realism? If that were the case I would think Bohmian mechanics would be much more popular! Instead it seems to me that both the Copenhagen interpretation (which abandons 'realism') and the Many-worlds interpretation (whose 'realist' status depends somewhat on how you define 'realism', but it is an interpretation that many advocates say is a completely local one, see my post #8 on this thread for some references along with my own toy model illustrating how a local interpretation involving multiple copies of each experimenter can explain Bell inequality violations without being non-local) are a lot more popular, see some of the polls linked to here.
Any chance you could post some of Einstein's quotes that you think show he was not a "naive realist" or would not have agreed with the ideas in the EPR paper? If it would take too long to find them and type them up, I will understand of course.
The EPR paper, say "EPR" for short, was not written, and not even given imprimatur by Einstein, who considered the effect of choosing a measurement, not the outcome of measurements in his own analysis of the completeness of QM. Einstein never used the elements of reality as defined in "EPR". The way "EPR" uses the elements of reality would permit to deduce Bell's ineauality and Richard Friedberg did that as I said and cited in the book of Jammer you emntioned. Yet "EPR" say that elements of reality should be rooted in experiments. If one consider together only what can be measured on ONE pair, then one has at most 2 projections of the spin (in the Bohm-Bell setting), i.e., one measurement per particle, hence not enough data to have a Bell type inequality.
B) Now Einstein had some dose of realism, but so did Heisenberg, Bohr, etc... Einstein gave in 1931 a proof that microscopic realism is false when Bohr and Heisenberg believed in retrodictive compatibility of exact values for conjugate variables. It is about time to not attribute the mistakes of "EPR" to Einstein. See the book of Fine (the Shaky game) beside the book of Jammer. You may find one or two citations of Einstein where he violates microscopic realism in the sense of observables pre-existing measurement (something that happens to have been proven experimentally for EPR particles, but not for enough observables at once to get a Bell type story, of course). Why should I follow you in defining microscopic in the incomplete way used by Podolsky in "EPR"? (since I consider that "It is about time to not attribute the mistakes of "EPR" to Einstein." ) Perhaps I'd be happy with the element of reality if you accept that measurement must be made on one particle at least for any value to make sense as Podolsky hints at but does not do. Invoking a great name for a mistake once may be ok, and even valuable (e.g., to relaunch an issue mistreated by that person where that was not noticed by anyone ), but assuming Einstein was really wrong on realism, why associate his name to that? It would be better to work on science than on means for people to prove themselves smarter that Einstein (not implying you do that, but there is a bad collective behavior).
(C) The situation is a bit more complex than that as most people who declares themselves as "non-realist" have been over the years convinced that the villain that causes the contradiction between Bell's inequalities and nature is locality. Bell did not state his theorem as proving QM non-local: he knew well what he was doing, but, again, read the beginning of his 1964 paper, where he implies that that QM had been proven non-local by "EPR". Now there are many more Bohmian than I feel comfortable with and Bell is their hero (see the writtings of Sheldon Goldstein). No if you want to drag me to coocoo land, I would tell you that when I almost died (which lasted a month at least) I could not believe in god, but could not get satisfaction in many world either. I'll see later you post #8 as my navigation prowess is very limited (which is why I hopped DrC would open a vouple of new thread or tell me where to learn how to do that, and why I asked how to upload a file so that I can give reference to it, or post it in some other way).
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