Analysis of Elliptically Polarized Maximally Entangled States for Bell Inequality Tests

TL;DR

This paper presents a theoretical and experimental method to optimize Bell inequality violations using elliptically polarized entangled states by phase compensation, enhancing quantum communication tests.

Contribution

It introduces a general approach for phase adjustment in elliptically polarized entangled states to maximize Bell inequality violations, including practical experimental implementation.

Findings

Phase compensation improves Bell violation measurements.

A simple phase correction scheme using Soleil-Babinet compensator is effective.

The approach is applicable to fiber-based quantum communication systems.

Abstract

When elliptically polarized maximally entangled states are considered, i.e., states having a non random phase factor between the two bipartite polarization components, the standard settings used for optimal violation of Bell inequalities are no longer adapted. One way to retrieve the maximal amount of violation is to compensate for this phase while keeping the standard Bell inequality analysis settings. We propose in this paper a general theoretical approach that allows determining and adjusting the phase of elliptically polarized maximally entangled states in order to optimize the violation of Bell inequalities. The formalism is also applied to several suggested experimental phase compensation schemes. In order to emphasize the simplicity and relevance of our approach, we also describe an experimental implementation using a standard Soleil-Babinet phase compensator. This device is employed to correct the phase that appears in the maximally entangled state generated from a type-II nonlinear photon-pair source after the photons are created and distributed over fiber channels.