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Physics
Quantum Physics
Quantum Interpretations and Foundations
Quantum Perspectivalism by D.Dieks
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[QUOTE="kurt101, post: 6837581, member: 611935"] There are violations of the Bell inequality that can be shown to violate locality and there are violations of the Bell inequality that can't be shown to violate locality. The author is calling attention to the later in the case where the outside photons (that I am calling Alice and Bob) are measured before the BSM test is done. Note, in no way is the author disputing the non-locality bell violation in two halves of the experiment in any of the cases. I am good with this statement when entangled means a violation of the Bell entanglement and does not imply direct non-local influences between 1 & 4. Agree. Agree with the caveat that the entanglement between 1 & 4 don't demonstrate direct non-local effects between 1 & 4 in the case where the BSM test is done after the measurement of 1 & 4. There are lots of photons at 1 & 4 that arrive at the same time that are candidates for being entangled. The experiment ignores any that don't show entanglement in the corresponding 2 & 3 at the BSM test. This process is what I mean by post selection. Obviously post selection is necessary to see the bell violation in all cases. I assume we agree on this. So I can agree that using the BSM along with the post selection process I just described is the cause / reason that photons 1 & 4 are entangled (have the Bell violation). I am sounding like a broken record at this point, but just to be clear what my point and what I think the author's point is, is that entanglement between 1 & 4 in the case where the BSM test is done after the measurement of 1 & 4 does not prove that there is a direct non-local influence between 1 & 4. I am not clear what you are saying here. Agree I think the quantum interaction (BSM test) is necessary because it is impossible to determine if the photons are otherwise truly identical by attempting to measure its properties. So I don't agree with your characterization "you should be able to simply post selection on identical quantum attributes" is possible. I don't understand your question here, but I explained what I mean by post-selection above. Ok I am afraid to use the term "acausal" because I was threatened with being kicked off the thread last time I used it even though I was just replying to your use of it. If you mean "not causal" then I think my objection remains, as I don't think the entanglement swapping experiment shows this for the reason the author of the paper we have been discussing brought up. What is your definition of Einstein causality. Is this a good definition (posted from google search): In both Einstein's theory of special and general relativity, causality means that [B]an effect cannot occur from a cause that is not in the back (past) light cone of that event[/B]. If this is what your definition is then I continue to disagree with you that the entanglement swapping experiment shows disagreement with this. I thought it was a hot topic of debate on whether there is an underlying model for Quantum mechanics. Though maybe I misunderstand you. I am always looking to understand why someone comes to this conclusion beyond just because nothing has been found yet. Except in the entanglement swapping experiment, it is also the BSM test that is relevant. I don't like doing that either and would have preferred to finish this in the thread that you created. Right now I just want to get a common understanding and ultimately the truth on this. I would like to respond to this as you are not understanding the argument I am making, but I have run out of time right now. I obviously realize you can't actually go in the reverse direction, but thinking of the experiment in the reverse direction makes it very apparent why you get the bell violation between 1 & 4 when the BSM measurement is made in the absolute future. [/QUOTE]
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