Quantum correlations of twophoton polarization states in the parametric down-conversion process

TL;DR

This paper investigates the effects of colored and white noise on two-photon polarization states in parametric down-conversion, analyzing quantum correlations, entanglement, and Bell inequality violations, with comparisons to experimental data.

Contribution

It introduces a model accounting for mixed noise types in polarization states and derives conditions for quantum correlations and separability in noisy environments.

Findings

Von Neumann entropy dependence on noise levels

Separability conditions derived using Peres-Horodecki and majorization criteria

Noise thresholds for Bell inequality violations

Abstract

We consider correlation properties of twophoton polarization states in the parametric down-conversion process. In our description of polarization states we take into account the simultaneous presence of colored and white noise in the density matrix. Within the considered model we study the dependence of the von Neumann entropy on the noise amount in the system and derive the separability condition for the density matrix of twophoton polarization state, using Perec-Horodecki criterion and majorization criterion. Then the dependence of the Bell operator (in CHSH form) on noise is studied. As a result, we give a condition for determining the presence of quantum correlation states in experimental measurements of the Bell operator. Finally, we compare our calculations with experimental data [doi:10.1103/PhysRevA.73.062110] and give a noise amount estimation in the photon polarization state considered there.