Entangled Two-Photon Wave Packet in a Dispersive Medium
  We report an experimental study of group-velocity dispersion effect on an entangled two-photon wavepacket, generated via spontaneous parametric down-conversion and propagating through a dispersive medium. Even in the case of using CW laser beam for pump, the biphoton wavepacket and the second-order correlation function spread significantly. The study and understanding of this phenomenon is of great importance for quantum information applications, such as quantum communication and distant clock synchronization. 
Alejandra Valencia, Maria V. Chekhova, Alexei Trifonov, and Yanhua   Shih