| 摘要 |
<P>PROBLEM TO BE SOLVED: To improve tolerance to a wiretapper by suppressing a loss of a reference light and decreasing an excessive noise ratio in homodyne detection. <P>SOLUTION: A quantum encryption communication apparatus 100 consists of a transmitter side terminal 1, a receiver side terminal 2, and a communication path 3. A reference light (pulse light P2) having a comparatively high strength and a weak signal light (pulse light P1) in which phase modulation is randomly applied per pulse are transmitted from the terminal 1 to the terminal 2. In the terminal 2, the reference light is subjected to random phase modulation per pulse, and then, homodyne detection is executed on the basis of the reference light and the signal light to acquire secret information, e. g. a secret key. In the terminal 2, a processing start timing of a phase modulator 7 is controlled on the basis of a synchronization signal to be supplied from a signal transmission source 17 for supplying a synchronization signal to the light source 4, and in the terminal 1, a detector 26 detects the arrival of the signal light to control a processing start timing of a phase modulator 21 on the basis of a leakage light from a variable attenuator 19. <P>COPYRIGHT: (C)2007,JPO&INPIT |
