Quantum correlations of two-photon polarization states in the parametric down-conversion in the presence of white and colored noise

Abstract

We consider correlation properties of two-photon polarization states in the parametric down-conversion process of type II. 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 two-photon 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 [4] and give a noise amount estimation in the photon polarization state considered there.