Weak Values are Interference Phenomena

TL;DR

Weak values in quantum mechanics are fundamentally interference phenomena, not just classical disturbance effects, as they involve uniquely quantum interference effects that cannot be replicated by classical models.

Contribution

The paper clarifies the quantum nature of weak values, emphasizing their role as interference phenomena and distinguishing them from classical disturbance effects.

Findings

Weak values can exceed eigenvalue ranges due to quantum interference.

Classical disturbance models cannot fully explain weak values without simulating quantum interference.

Weak values serve as both conditioned estimates and dynamical variables in quantum systems.

Abstract

Weak values arise experimentally as conditioned averages of weak (noisy) observable measurements that minimally disturb an initial quantum state, and also as dynamical variables for reduced quantum state evolution even in the absence of measurement. These averages can exceed the eigenvalue range of the observable ostensibly being estimated, which has prompted considerable debate regarding their interpretation. Classical conditioned averages of noisy signals only show such anomalies if the quantity being measured is also disturbed prior to conditioning. This fact has recently been rediscovered, along with the question whether anomalous weak values are merely classical disturbance effects. Here we carefully review the role of the weak value as both a conditioned observable estimation and a dynamical variable, and clarify why classical disturbance models will be insufficient to explain the weak value unless they can also simulate other quantum interference phenomena.