Reply To: Causality and quantum mechanics (Online 7/15 @ 10 p.m. to Midnight UTC-7)

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#2849
David MillerDavid Miller
Participant

Hi Ken

Thanks for your comments. We will clarify the “switching” of A and B is not different time directions and include more references!

Yes, I think our paper is neutral with respect to ontic/epistemic.

I agree the distinction (if any!?) between “cause” and “correlator” needs further thought and elaboration. If Alice re-flips a fair coin she knows she has done that but nobody else (who hasn’t watched her, etc) can find out whether she has or not. Under those circumstances, is it correct to say the coin carries a “causal influence” due to the re-flip? More generally, if p^B(j) is not changed, B cannot tell whether C was performed or not so there can be no evidence of a causal influence from B’s results alone. On the other hand p^{AB}(i\&j) can be changed by C – evidence of correlation.

Of course Alice carries a record of the re-flip but she didn’t start out in a maximally mixed state. It is true that C is independent of the state it acts on but isn’t it possible even classically that the same operation can be a cause under some circumstances but not others?

Finally, the bipartite states in Sect. IV are general – can be product, partitally entangled or maximally entangled.

Cheers

David

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