Time Symmetric Quantum Theory Without Retrocausality? A Reply to Tim Maudlin

TL;DR

This paper defends a no-retrocausality theorem in quantum mechanics by analyzing a counterexample proposed by Maudlin, clarifying misunderstandings about the assumptions and the validity of the original proof.

Contribution

The paper clarifies why Maudlin's proposed model does not violate the no-retrocausality theorem and corrects misconceptions about the proof's lemmas.

Findings

Maudlin's model does not satisfy the original time-symmetry assumption.

The original lemma used in the proof remains valid.

Maudlin's claim of a counterexample is unfounded.

Abstract

In arXiv:1707.08641, Tim Maudlin claims to construct a counterexample to the result of Proc. Roy. Soc. A vol. 473, iss. 2202, 2017 (arXiv:1607.07871), in which it was shown that no realist model satisfying a certain notion of time-symmetry (in addition to three other assumptions) can reproduce the predictions of quantum theory without retrocausality (influences travelling backwards in time). In this comment, I explain why Maudlin's model is not a counterexample because it does not satisfy our time-symmetry assumption. I also explain why Maudlin's claim that one of the Lemmas we used in our proof is incorrect is wrong.