Experimental investigation of nonclassicality in the simplest scenario via the degrees of freedom of light

TL;DR

This paper experimentally explores nonclassicality in a simple prepare-and-measure setup using classical light, demonstrating violations of noncontextuality inequalities and relevance for quantum communication tasks.

Contribution

It provides the first experimental demonstration of nonclassicality violations in the simplest scenario with classical light, using multiple degrees of freedom and noise modeling.

Findings

Violations of noise-robust noncontextuality inequalities observed

Classical light reproduces quantum scenario statistics

Implications for semi-device-independent quantum communication

Abstract

In this work, we experimentally investigate the classical-light emulation of different notions of nonclassicality in the simplest scenario. We implement this prepare-and-measure scenario involving four preparations and two binary-outcome measurements using two distinct experimental setups that exploit different degrees of freedom of light: polarization and first-order Hermite-Gaussian transverse modes. We additionally model experimental noise through an all-optical setup that reproduces the operational effect of a depolarizing channel. Our experimental results are consistent with the findings of Khoshbin et al. [Phys. Rev. A 109, 032212 (2024)]: under the assumption that the two measurements performed form a tomographically complete set, the observed statistics violate their noise-robust inequalities, indicating inconsistencies with preparation noncontextuality and bounded ontological distinctness for preparations. Although our implementation uses classical light, it reproduces the statistics predicted for the simplest scenario. Since the states and measurements of this scenario underpin computational advantages in tasks such as two-bit quantum random access codes -- among the simplest communication primitives enabling semi-device-independent certification of nonclassicality -- our implementation is directly relevant for such applications.