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 transf ormations. The fidelity and indices of quantum correlations based on the vo n 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 dis persion and absorption, the quantum correlations are reduced, and they decr ease with increasing initial entanglement. (C) 2001 MAIK "Nauka/Interperiod ica".