Weak-value amplification: state of play

TL;DR

This paper reviews the current understanding of weak-value amplification in quantum measurement, highlighting conflicting theoretical and experimental findings on its effectiveness for improving quantum sensor performance.

Contribution

It provides a comprehensive survey of recent theoretical and experimental studies on weak-value amplification, emphasizing the need to reconcile differing conclusions.

Findings

Weak values can produce significant signal amplification in quantum measurements.

Recent theory suggests weak-value amplification may reduce measurement precision.

Experimental results show potential benefits, but theoretical analysis questions their overall utility.

Abstract

Weak values arise in quantum theory when the result of a weak measurement is conditioned on a subsequent strong measurement. The majority of the trials are discarded, leaving only very few successful events. Intriguingly those can display a substantial signal amplification. This raises the question of whether weak values carry potential to improve the performance of quantum sensors, and indeed a number of impressive experimental results suggested this may be the case. By contrast, recent theoretical studies have found the opposite: using weak-values to obtain an amplification generally worsens metrological performance. This survey summarises the implications of those studies, which call for a reappraisal of weak values' utility and for further work to reconcile theory and experiment.