Experimental test of contextuality in quantum and classical systems

TL;DR

This paper experimentally investigates the manifestation of contextuality in quantum and classical optical fields, emphasizing how measurement definitions influence the observation of non-classical correlations.

Contribution

It demonstrates that contextuality in classical fields depends on measurement definitions, linking it to non-classicality via phase space quasi-probabilities.

Findings

Heralded single photon states show contextuality.

Classical coherent fields' contextuality depends on measurement filtering.

Measurement definitions critically affect observed contextuality.

Abstract

Contextuality is considered as an intrinsic signature of non-classicality, and a crucial resource for achieving unique advantages of quantum information processing. However, recently there have been debates on whether classical fields may also demonstrate contextuality. Here we experimentally configure a contextuality test for optical fields, adopting various definitions of measurement events, and analyse how the definitions affect the emergence of non-classical correlations. The heralded single photon state, a typical non-classical light field, manifests contextuality in our setup, while contextuality for classical coherent fields strongly depends on the specific definition of measurement events which is equivalent to filtering the non-classical component of the input state. Our results highlight the importance of definition of measurement events to demonstrate contextuality, and link the contextual correlations to non-classicality defined by quasi-probabilities in phase space.