Free-space quantum key distribution with entangled photons

The authors report on a complete experimental implementation of a quantum key distribution protocol through a free-space link using polarization-entangled photon pairs from a compact parametric downconversion source. Over 10 h of uninterrupted communication between sites 1.5 km apart, they observe average key generation rates of 630/s after error correction and privacy amplification. Their scheme requires no specific hardware channel for synchronization apart from a classical wireless link, and no explicit random number generator. (c) 2006 American Institute of Physics.