Bell-like inequality for spin-orbit separability of a classical laser beam

TL;DR

This paper introduces a Bell-like inequality for classical laser beams' spin-orbit modes, demonstrating its violation for non-separable modes both theoretically and experimentally, and discusses implications for classical-quantum transition.

Contribution

It proposes a new inequality criterion for classical spin-orbit non-separability inspired by Bell's inequality, validated through experiments.

Findings

The inequality is violated by non-separable modes.

Experimental validation confirms theoretical predictions.

Discusses implications for classical-quantum boundary.

Abstract

In analogy with Bell's inequality for two-qubit quantum states we propose an inequality criterion for the non-separability of the spin-orbit degrees of freedom of a classical laser beam. A definition of separable and non-separable spin-orbit modes is used in consonance with the one presented in Phys. Rev. Lett. 99, 160401 (2007). As the usual Bell's inequality can be violated for entangled two-qubit quantum states, we show both theoretically and experimentally that the proposed spin-orbit inequality criterion can be violated for non-separable modes. A discussion on the classical-quantum transition is also presented.