Abstract: Provided are a method and a device for quantum key distribution. The quantum key distribution device may be connected to another quantum key distribution device through a quantum channel and distribute a quantum cryptography key. The device may include an optical unit having an optical element to transmit information, and a post-processor for calculating a quantum cryptography key by processing a random number generated by the optical unit. The device may include at least one of the optical unit including a plurality of unit optical modules, the post-processor having a plurality of unit post-processing modules, and the optical unit having a plurality of unit optical modules and the post-processor having a plurality of unit post-processing modules.

Abstract: Provided are a single photon detector and an operation method thereof. The single photon detector may include a gate signal generator for generating a gate signal having a first pulse width (?P) with respect to a first time point (t1); and a first photon detector for detecting the single photon while operating in a Geiger mode by receiving the gate signal, and outputs a photon detection signal at a second time point (t2), wherein the first photon detector outputs the photon detection signal at the second time point (t2) spaced apart at a predetermine time interval (?T) from the first time point (t1).

Abstract: Provided are a quantum key distribution method, device, and system. The quantum key distribution system may include a transmitter configured to split an optical signal into a first optical signal passing through a first path (P1) and a second optical signal passing through a second path (P2), which is longer than the first path (P1), and to sequentially transmit the first optical signal and the second optical signal; and a receiver configured to receive the first optical signal and the second optical signal incident through a quantum channel and transmit the first optical signal and the second optical signal back to the transmitter through the quantum channel after passing through a polarization-dependent element, being reflected by a Faraday mirror, and passing through the polarization-dependent element again.