James Ladyman (Bristol): What are Weak Values?

James Ladyman (Bristol)

Title: What are Weak Values

Abstract: This paper is about the philosophical interpretation and implications of weak values in quantum mechanics. In particular; we present an argument for a subtle kind of retrocausality (which we define as the causal dependence of earlier events on later events) that is based on the probabilistic structure of experiments to determine weak values that we explain. We consider what type of property weak values are; and explain some of their unusual features and how they relate to the nature of the retrocausality they exhibit; and we briefly consider the merits of the two-state vector approach to weak values; and explore how they should be understood in the context of Everettian quantum mechanics.