>> your claim that the QM description is not correct
> That's not my claim. My claim is that the change in the mathematical description of Bob's particles (from mixed states to pure states) when Alice measures her particles does not correspond to any actual physical change in Bob's particles.
Well, according to quantum mechanics there is a physical change when Alice measures her particles because:
before Alice's measurement => the pair "A/B" is entangled
after Alice's measurement => the pair "A/B" is not entangled
According to you alternative description, is the pair A/B entangled or not after Alice's measurement? Or is entanglement not an actual physical property of the pair?
I am (or used to be, for a brief time many years ago) a physicist. We had the opportunity to discuss in person last week. I enjoyed that (and this) discussion, thanks. By the way, I said I would send you a comment from David Mermin about the recent paper from Frauchiger and Renner. Actually I was thinking about this article from Jeffrey Bub: https://arxiv.org/abs/1804.03267
> Well, according to quantum mechanics there is a physical change when Alice measures her particles because:
> before Alice's measurement => the pair "A/B" is entangled
> after Alice's measurement => the pair "A/B" is not entangled
No. That's the whole point. The presence of absence of entanglement is a function of the perspective you choose to take when modeling the situation, not a function of the actual physical situation.
Thanks for the pointer to the Bub paper, that's a great reference.
Maybe we should move this discussion to email? It's getting pretty deeply nested and I don't think anyone else is paying attention.
> That's not my claim. My claim is that the change in the mathematical description of Bob's particles (from mixed states to pure states) when Alice measures her particles does not correspond to any actual physical change in Bob's particles.
Well, according to quantum mechanics there is a physical change when Alice measures her particles because:
before Alice's measurement => the pair "A/B" is entangled
after Alice's measurement => the pair "A/B" is not entangled
According to you alternative description, is the pair A/B entangled or not after Alice's measurement? Or is entanglement not an actual physical property of the pair?
I am (or used to be, for a brief time many years ago) a physicist. We had the opportunity to discuss in person last week. I enjoyed that (and this) discussion, thanks. By the way, I said I would send you a comment from David Mermin about the recent paper from Frauchiger and Renner. Actually I was thinking about this article from Jeffrey Bub: https://arxiv.org/abs/1804.03267