Generation and characterization of a source of wavelength division   multiplexing quantum key distribution
  Using spontaneous parametric down-conversion, photon pairs entangled in frequency and polarization were generated. After frequency resolving the photon pairs, the polarization correlations were measured on several polarization basis, and it was confirmed that the frequency resolved photon pairs were entangled in polarization, indicating the photon pairs can be used as a source of wavelength division multiplexing quantum key distribution. 
Atsushi Yabushita, Takayoshi Kobayashi