Propagation of entangled light pulses through dispersive and absorbing   channels
  The modification of initially entangled light pulses passing through dispersive and absorbing four-port devices is studied, using recently obtained results on quantum state transformations [Phys. Rev. A 59, 4716 (1999)]. 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 substantially for large initial entanglement. 
A.V. Chizhov, E. Schmidt, L. Knoll, and D.-G. Welsch