# Single-photon spin-orbit entanglement violating a Bell-like inequality

## TL;DR

This paper demonstrates that single photons with entangled spin and orbital angular momentum can violate Bell-like inequalities, providing evidence against noncontextual hidden variable theories using an experimental scheme.

## Contribution

It proposes an experimental method to test spin-orbit entanglement in single photons and shows violation of Bell-like inequalities.

## Key findings

- CHSH parameter S up to 2.828 observed
- Violates Bell-like inequality confirming quantum entanglement
- Challenges noncontextual hidden variable theories

## Abstract

Single photons emerging from q-plates (or Pancharatnam-Berry phase optical element) exhibit entanglement in the degrees of freedom of spin and orbital angular momentum. We put forward an experimental scheme for probing the spin-orbit correlations of single photons. It is found that the Clauser-Horne-Shimony-Holt (CHSH) parameter S for the single-photon spin-orbit entangled state could be up to 2.828, evidently violating the Bell-like inequality and thus invalidating the noncontextual hidden variable (NCHV) theories.

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Source: https://tomesphere.com/paper/0911.0544