local wrote:It's just the standard quantum woo-woo nonsense. The bottom line is that no experiment has ever proved quantum nonlocality, despite all the claims.
Q-reeus wrote:How can locality possibly hold given there is also completely random measurements at either detector?
minkwe wrote:Q-reeus wrote:How can locality possibly hold given there is also completely random measurements at either detector?
What do you mean by completely random measurements at either detector? That statement is too vague. You will need to explain further.
Q-reeus wrote:Just what is mentioned in that vid - given the orthogonality between detector angle and spin axes, there is a 50:50 chance of either spin up or spin down measurement, at any one detector. That much is intuitively obvious. It's the perfect anti-correlations that are troublesome for any local realist interpretation.
minkwe wrote:I'm just not sure why you single out local realistic interpretations. What about QM? Do the bell-test experiments confirm the perfect anti-correlation? If not then why should it be a problem for local realism and not QM?
You should ask the question of QM. How is it possible to have perfect anti-correlations and yet random outcomes at each station. That is what QM says.
Q-reeus wrote:I haven't so far come across an actual Bell experiment coinciding with that example given.
Q-reeus wrote:
It's the perfect anti-correlations that are troublesome for any local realist interpretation.
local wrote:The perfect anti-correlation is easy to duplicate classically. The sawtooth and the cosine correspond at some points and aligned detectors is one of those points....
I can generate a pair of cards, one white and one black, with 50% probability for white-black and black-white. When I send one card to each of two sides they will always be anticorrelated but each side sees random black/white.
inherent, fundamentally physical measurement randomness at each detector
Q-reeus wrote:Stacking the decks like that is entirely artificial and ignores the inherent randomness of spin-up vs spin-down for orthogonal spin-detector orientation.
To correspond to the actual situation referred to in vid, your example should have been of cards each with one face white and the opposite face black. Part the cards in opposite directions, but with a perfect initial anti-correlation such that say a white face on one mates to a white face on the other card. But when detected re black or white face showing, each detector is vibrating such that it randomly flips each received card 50:50 black face or white face 'detected'.
Joy Christian wrote:Q-reeus wrote:
It's the perfect anti-correlations that are troublesome for any local realist interpretation.
There is nothing mysterious going on here. Anit-correations are not a problem for local realistic interpretation. I watched a few minutes of the video from 2:20. The guy does not understand even the most basic facts about the EPRB correlations. No experimental complications or randomness definitions are necessary to understand his mistake. There is perfect anti-correlation even in Dr. Bertlmann's socks, as Bell used to point out fondly.
Imagine you are walking from your home in winter and midway to your destination you reach out your pockets for hand-gloves, but you find only one of them. At that moment you instantly know that you forgot the other one at home. Not only do you know that, but you also instantly know that the one you forgot at home is a lefthand glove if the one you pulled out from your pocket happens to be a righthand glove. Note that this is true even if your home happens to be in the far corner of the Universe. You have instant information about the handedness of the glove you forgot at home by simply looking at the glove you just pulled out from your pocket. That is perfect anti-correlation and it has nothing to do with nonlocality of any sort. It is just simple classical physics. The same is true for the anti-correlation of spins in the EPRB setup.
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Q-reeus wrote:Well someone(s) has wrong thinking on this. Instead of addressing either of the last few posts individually, I'll just refer respondents back to the middle para of first post.
To repeat yet again - overall conservation of angular momentum is not an answer. If locality in QM holds, conservative exchanges of angular momenta between each particle and each detector should be an entirely local affair quite independent of any initial correlations between the particle pair. With 50:50 chance of spin-up vs spin-down detection - at each detector separately.
Consequently, assuming QM obeys locality, spin measurement at detector A should have no statistical correlation with the measurement at detector B. Given the specified settings.
Viz - parallel or anti-parallel detector orientations, coupled with orthogonal orientations between each detector and incident spin 1/2 particle. Yet actually perfect anti-correlations result according to QM.
Is that hard to grasp?
FrediFizzx wrote:Conservation of angular momentum is exactly the answer. Here are a couple different treatments of how QM is local for the EPR-Bohm scenario.
viewtopic.php?f=6&t=409
viewtopic.php?f=6&t=412
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Q-reeus wrote:Well someone(s) has wrong thinking on this. Instead of addressing either of the last few posts individually, I'll just refer respondents back to the middle para of first post.
To repeat yet again - overall conservation of angular momentum is not an answer. If locality in QM holds, conservative exchanges of angular momenta between each particle and each detector should be an entirely local affair quite independent of any initial correlations between the particle pair. With 50:50 chance of spin-up vs spin-down detection - at each detector separately.
Consequently, assuming QM obeys locality, spin measurement at detector A should have no statistical correlation with the measurement at detector B. Given the specified settings.
Viz - parallel or anti-parallel detector orientations, coupled with orthogonal orientations between each detector and incident spin 1/2 particle. Yet actually perfect anti-correlations result according to QM.
Is that hard to grasp?
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