Two-pulse correlations in noisy quantum channels

The modification of initially entangled light pulses passing through noisy quantum channels, modeled by dispersive and absorbing four-port devices, is studied with the help of recently obtained results on quantum state transformations. The fidelity and indices of quantum correlations based on the von Neumann entropy are calculated. Their dependence on both the pulse shape and the four-port device parameters is studied. It is shown that due to dispersion and absorption, the quantum correlations are reduced, and they decrease with increasing initial entanglement.