Weak values are quantum: you can bet on it

TL;DR

This paper investigates the quantum nature of weak values, demonstrating through a simple quantum model which features are genuinely quantum and cannot be explained classically, clarifying ongoing debates in quantum measurement theory.

Contribution

The paper provides a simple quantum model to distinguish quantum features of weak values from classical explanations, clarifying what makes weak values inherently quantum.

Findings

Classical models can produce non-trivial conditional values similar to weak values.

Certain features of weak values are uniquely quantum and cannot be replicated classically.

The paper outlines key open questions in the current research on weak values.

Abstract

The outcome of a weak quantum measurement conditioned to a subsequent postselection (a weak value protocol) can assume peculiar values. These results cannot be explained in terms of conditional probabilistic outcomes of projective measurements. However, a classical model has been recently put forward that can reproduce peculiar expectation values, reminiscent of weak values. This led the authors of that work to claim that weak values have an entirely classical explanation. Here we discuss what is quantum about weak values with the help of a simple model based on basic quantum mechanics. We first demonstrate how a classical theory can indeed give rise to non-trivial conditional values, and explain what features of weak values are genuinely quantum. We finally use our model to outline some main issues under current research.