Quantum key distribution for continuous variable by means of phase-sensitive nondegenerate optical parametric amplifier

A new protocol realizing quantum key distribution for continuous variables is proposed, in which the bright entangled EPR beams are produced from a phase-sensitive nondegenerate optical parametric amplifier. Based on randomly changing the operating states of NOPA at the sending station and randomly choosing the phase difference between two modes of EPR beams at the receiving station, the secret key string is established. The application of direct detection system of photocurrents makes the proposed scheme relatively easier to be experimentally demonstrated.