Evaluation of two-photon polarization density matrix of polarization-entangled photon pairs generated through biexciton resonant hyper-parametric scattering

摘要

We have investigated the excitation-power dependence ofpolarization-entangled photon-pairs generated from a CuCl single crystal usingbiexciton resonant hyper-parametric scattering. The measured two-photonpolarization density matrix which corresponds to the two-photon polarizationstate changes with increasing the excitation power. The evaluation of thetangle and the linear entropy obtained from the measured density matrixindicates that the two-photon polarization density matrix can be expressed asthe mixed state of an ideal state and a totally mixed state, and the mixtureratio of the totally mixed state increases as the excitation density increases.The variations of the density matrix and the mixture ratio with the excitationpower originate from the generation of the multiple photon pairs.