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msumm21
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- TL;DR Summary
- The explanation of Bell violations in this book, according to relational QM, doesn't make sense to me
On pages 94-96 of Helgoland, Rovelli explains Bell violations according to relational QM. He speaks of spacelike separated measurements, one in Beijing and the other in Vienna. He says any talk of correlations between the 2 is meaningless, specifically:
"it makes no sense to ask whether the two results are the same or not."
He later says of the measurements:
"we cannot assume that both exist, because there is nothing with respect to which both can be determined."
He explains that the result in Vienna is not real in Beijing until a signal about it arrives in Beijing, and vice versa.
I'm not clear what he means about one of the measurements not being real or not existing, while the other is real and exists. Consider Alice in Beijing measuring one particle. So her particle's spin exists and is real, while Bob's in Vienna is not? Alice doesn't "directly" see the spin of her particle in Beijing, she only sees the result after that particle has entangled with many things to magnify the result to readable measurement. So I'm not clear why her particle & result is "real" after that chain of thousands (millions?) of entanglements, but then making just 1 more inference from entanglement (that the entangled particle in Vienna has the opposite spin) is somehow no good.
How does relational QM decide where to draw this line between which entanglements are valid to use for inference of reality and which are bogus?
"it makes no sense to ask whether the two results are the same or not."
He later says of the measurements:
"we cannot assume that both exist, because there is nothing with respect to which both can be determined."
He explains that the result in Vienna is not real in Beijing until a signal about it arrives in Beijing, and vice versa.
I'm not clear what he means about one of the measurements not being real or not existing, while the other is real and exists. Consider Alice in Beijing measuring one particle. So her particle's spin exists and is real, while Bob's in Vienna is not? Alice doesn't "directly" see the spin of her particle in Beijing, she only sees the result after that particle has entangled with many things to magnify the result to readable measurement. So I'm not clear why her particle & result is "real" after that chain of thousands (millions?) of entanglements, but then making just 1 more inference from entanglement (that the entangled particle in Vienna has the opposite spin) is somehow no good.
How does relational QM decide where to draw this line between which entanglements are valid to use for inference of reality and which are bogus?