| 摘要 |
PROBLEM TO BE SOLVED: To provide a quantum key distribution system of a new principle.SOLUTION: A transmitter transmits an optical pulse train of length-L pulses with less than one photon per pulse on the average. When the optical pulse train is inputted to an interferometer, a receiver detects one photon in an (m+k)th pulse. Whether the detection is made successful is discriminated on the basis of whether one photon is a multiplexed wave of two optical pulses at the interferometer. If the detection is made successful, a bit value is recorded in accordance with whether phase shifts of the multiplexed two optical pulses are different or not, and a result of the success or failure and numbers (m, m+k) of the two optical pulses are transmitted to the transmitter. On the basis of (m, m+k), the transmitter extracts two bit values corresponding to the numbers (m, m+k) out of the transmitted optical pulse train, and different bit values are recorded in accordance with whether the two bit values are different or not. In the case where N times of successes are discriminated while optical pulse trains are inputted M times, a value S(N) for confidentiality enhancement is determined and the confidentiality enhancement is implemented by subtracting S(N) bits from N pieces of bit trains which are recorded at the transmitter and the receiver, such that the transmitter and the receiver share a secret key.SELECTED DRAWING: Figure 2 |
