Orthogonal and polarization-entangled photon-pair arrangement for decoherence-free quantum measurement

A theoretical model is presented for the interaction of a quantum system with an orthogonal polarized entangled photon-pair measurement probe. The theoretical framework is based on solving the generalized Jaynes-Cummings and Shroeder's equations to determine the phase evolution of the interacting system. The measurement-induced decoherence is expressed in terms of the temporal evolution of the relative phases of the superposition states induced by the measurement probe. The method is applied to determine the rate of decoherence of a two-qubit rubidium quantum system. Quantitative results are given to contrast measurement-induced of (i) single photon probe and (ii) orthogonal polarized and entangled probe.