Theory of Quantum Entanglement of Intra-Cavity Photons Produced by a Non-Degenerate Parametric Oscillator (Ndpo) Semi-Classical Approach

Abstract

The von-Neumann entropy (VNE), usually expressed in terms of the density operator, isthe mathematical tool to measure the degree of entanglement of a bi-partite system.Applying the solutions of the quantum Langevin equations, the anti-normally orderedcharacteristic function of the intra-cavity photons produced by a non-degenerateparametric oscillator could be calculated. With the help of the resulting characteristicfunction, the Q- function which is then used to calculate the entanglement of the intra-cavity photons using VNE is determined. Moreover, the photon number distribution, themean photon number, the normalized second order correlation function, the intensitydifference, and quadrature variance for the intra-cavity photons produced by a non-degenerate parametric oscillator coupled to a two-mode squeezed vacuum reservoir isdetermined. It was found that when the squeeze parameter increases the entanglement alsoincreases. These show that the entropy entanglement has a direct relation with squeezing.