Quantum key distribution at telecom wavelengths with noise-free detectors

The length of a secure link over which a quantum key can be distributed depends on the efficiency and dark-count rate of the detectors used at the receiver. We report on the first demonstration of quantum key distribution using superconducting transition-edge sensors with high efficiency and negligible dark-count rates. Using two methods of synchronization, a bright optical pulse scheme and an electrical signal scheme, we have successfully distributed key material at 1550 nm over 50 km of optical fiber. We discuss how use of these detectors in a quantum key distribution system can dramatically increase range and performance. (c) 2006 American Institute of Physics.