Hi Ken

As a classical example of something sometimes being a cause and sometimes not, I think of the proverbial butterfly in the Amazon jungle causing a hurricane – sometimes it does but mainly it doesn’t.

I think you can only go so far with classical intuitions about quantum causes because as we have found out from nonlocality, etc “co…[Read more]

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 s…[Read more]

Dear Bob

Thanks very much for your interest and comments. I agree with your reasoning entirely. You have raised valid points about temporal (ir)reversibility which is perfectly understandable because our submission is under the Topic “Time-symmetric theories”. But our submission, and I think some other of the submissions here, aren’t really purpo…[Read more]

Hi Pete

Thanks for your interesting paper. For what it’s worth I vote for Fig. 4 of your paper.

I got a bit stuck on Sect. 4.2. How do we choose the values of $ alpha_2$ and $beta_2$? Do we have to anticipate what angles we are going to choose in other repetitions of the experiment?

On a more general note, is there any mileage in thinking a…[Read more]

Hi Michael

Fortunately the case we consider avoids the situation you refer to. For example, your example does not begin with a maximally mixed state and it is implicit in our case that each member of the ensemble is available for A, B and C to be performed on them.

When considering transitions, as your example does, the role of final states is a…[Read more]

Hi Daniel Rohrlich

Firstly and with respect, I am very enthusiastic about your idea of using “the existence of a classical limit” as an axiom. Apart from the fact that you have shown it to be fruitful, I think it strengthens physicists’ “grip on reality” which seems to be being progressively loosened.

I have a few questions/comments about you…[Read more]

Hi Michael

Thanks for your question – it’s good to have a chance to try to explain in informal language.

We’re trying to see what QM per se can tell us about causality. For example, where in the algebra is retrocausality ruled out (if it is)? We know the joke about a physicist being asked to come up with a theory about horses in a paddock, the n…[Read more]