Introduction to Quantum Cryptography and the Tokyo QKD Network

Quantum cryptography、consisting of quantum key distribution (QKD) and one-time pad encryption, allows for communication with unconditional security. In QKD systems, the senders encode information on single photons one by one, while the receivers measure the photon states and decode the information. By distilling possible eavesdropped bits, secure keys can be shared between the senders and receivers. Tokyo QKD Network, into which various quantum key distribution systems were integrated through cross platform, established upon NICT's test bed ("JGN2plus"). We have succeeded in the key-relay and the rerouting experiment using Tokyo QKD Network.