Violation of the Leggett-Garg inequality with weak measurements of photons

TL;DR

This paper experimentally demonstrates that weak measurements of photon polarization can violate the Leggett-Garg inequality, linking anomalous weak values to the violation of macrorealism and non-intrusiveness in quantum systems.

Contribution

It provides the first experimental violation of the Leggett-Garg inequality using weak measurements of photons, establishing a direct correlation between strange weak values and macrorealism violation.

Findings

Violations of the Leggett-Garg inequality observed for various measurement strengths.

A one-to-one correlation between anomalous weak values and inequality violation.

Experimental evidence supporting quantum non-classicality in photon polarization measurements.

Abstract

By weakly measuring the polarization of a photon between two strong polarization measurements, we experimentally investigate the correlation between the appearance of anomalous values in quantum weak measurements, and the violation of realism and non-intrusiveness of measurements. A quantitative formulation of the latter concept is expressed in terms of a Leggett-Garg inequality for the outcomes of subsequent measurements of an individual quantum system. We experimentally violate the Leggett-Garg inequality for several measurement strengths. Furthermore, we experimentally demonstrate that there is a one-to-one correlation between achieving strange weak values and violating the Leggett-Garg inequality.