Spin-orbit hybrid entanglement of photons and quantum contextuality

TL;DR

This paper reports the creation of hybrid entangled states of single photons and photon pairs involving spin and orbital angular momentum, demonstrating quantum contextuality and non-locality through inequality violations.

Contribution

It introduces a method to generate and verify hybrid spin-orbit entanglement in photons using a q-plate, including a classical analog demonstration.

Findings

Violation of CHSH inequality confirms quantum entanglement and contextuality.

Successful generation of hybrid spin-orbit entangled photon states.

Identification of a classical analog for quantum spin-orbit entanglement.

Abstract

We demonstrate electromagnetic quantum states of single photons and of correlated photon pairs exhibiting "hybrid" entanglement between spin and orbital angular momentum. These states are obtained from entangled photon pairs emitted by spontaneous parametric down conversion, by employing a $q$-plate for coupling the spin and orbital degrees of freedom of a photon. Entanglement and contextual quantum behavior (that is also non-local, in the case of photon pairs) is demonstrated by the reported violation of the Clauser-Horne-Shimony-Holt inequality. In addition a classical analog of the hybrid spin-orbit photonic entanglement is reported and discussed.