Quantum channel using photon number correlated twin beams
  We report quantum communications channel using photon number correlated twin beams. The twin beams are generated from a nondegenerate optical parametric oscillator, and the photon number difference is used to encode the signal. The bit error rate of our system will be 0.067 by using the twin beams comparing with 0.217 by using the coherent state as the signal carrier. 
Yun Zhang, Katsuyuki Kasai, and Kazuhiro Hayasaka