Pancharatnam phase in non-separable states of light

TL;DR

This paper explores how the Pancharatnam geometric phase affects non-separable light states, demonstrating its influence on Bell inequality violations and how measurement basis choice impacts this relationship.

Contribution

It experimentally investigates the impact of Pancharatnam phase on Bell-CHSH inequality violations in non-separable polarization and OAM states of light.

Findings

Bell-CHSH parameter oscillates with Pancharatnam phase in linear bases.

Introducing a relative phase can mitigate phase dependence in linear bases.

In circular bases, the Pancharatnam phase does not affect Bell-CHSH violation.

Abstract

We generate the non-separable state of polarization and orbital angular momentum (OAM) using a laser beam. The generated state undergoes a cyclic polarization evolution which introduces a Pancharatnam geometric phase to the polarization state and in turn a relative phase in the non-separable state. We experimentally study the violation of Bell - CHSH inequality for different Pancharatnam phases introduced by various cyclic polarization evolutions with linear and circular states as measurement bases. While measuring in linear bases, the Bell-CHSH parameter oscillates with Pancharatnam phase. One can overcome this dependence by introducing a relative phase in one of the projecting state. However for measurement in circular bases, the Pancharatnam phase does not affect the Bell-CHSH violation.