Patent ID: 8923517
Filing Date: 2014-12-30
Classification: H04L

Abstract:
1. A multi-terminal quantum key distribution system comprising: a quantum entangled photon pair generating device; an optical frequency dividing filter; a 2N-input/2N-output optical switch; a 2N number of quantum key receiving devices; and a control unit, wherein N is an integer of two or more, and f bit/s is an assumed maximum key generation rate of a quantum encryption key, the quantum entangled photon pair generating device generates quantum entangled photon pairs having an optical frequency region of at least 2Nf Hz, the optical frequency dividing filter has a 2N number of output ports, receives the quantum entangled photon pairs output from the quantum entangled photon pair generating device, divides the optical frequency region by 2N, and outputs photons of the 2N number of optical frequency regions from the 2N number of output ports, the 2N-input/2N-output optical switch receives the photons of the 2N number of optical frequency regions output from the 2N number of output ports of the optical frequency dividing filter, allocates each of the photons of the 2N number of optical frequency regions to any one of the 2N number of output ports, and outputs the photons, each of the 2N number of quantum key receiving devices includes a signal processing circuit and detects each of the photons of the 2N number of optical frequency regions output from the 2N-input/2N-output optical switch, and the signal processing circuit receives measurement basis information that is sent from the other quantum key receiving devices via a classical channel, sends the measurement basis information to the other quantum key receiving devices via the classical channel, determines time information at which measurement bases of a sender and a receiver match, sends the determined time information to the other quantum key receiving devices via the classical channel, and generates a sifted key by leaving only a photon bit measured at a time at which the measurement bases match, and the control unit controls an operation of the 2N-input/2N-output optical switch, and controls a sifted key generation process in each of the quantum key receiving devices through the classical channel.