NTT Basic Research Laboratories through collaborative research with the Stanford branch of the National Institute of Informatics (NII) and the National Institute of Standards and Technology (NIST) have developed a quantum cryptography system with world’s fastest 10 GHz clock and have succeeded in realizing a quantum key distribution using single photon level light over a long (200 km) optical fiber in a laboratory. This achievement was realized by combining the high clock ready differential phase shift-quantum key distribution technology developed by NTT Basic Research Laboratories and the Stanford branch of NII with an ultra-sensitive and high-temporal resolution superconductive single photon detector developed by NIST.

  This is expected to constitute important basic technology for realizing an ultimately secure long-distance communication network that excludes eavesdropping.

This achievement will be published in the English science journal “Nature Photonics” on July, 1.

=> Quantum Optical State Control Research Group

Fig. 1 Quantum cryptography system with 10GHz clock
(SSPD: Superconductive Sigle Photon Detector)

 Fig. 2 Transmission loss (fiber length) vs Secure key generation rate