title: Secure quantum key distribution with an uncharacterized source.
abstract: We prove the security of the Bennett-Brassard (BB84) quantum key distribution protocol for an arbitrary source whose averaged states are basis independent, a condition that is automatically satisfied if the source is suitably designed. The proof is based on the observation that, to an adversary, the key extraction process is equivalent to a measurement in the sigma(x) basis performed on a pure sigma(z)-basis eigenstate. The dependence of the achievable key length on the bit error rate is the same as that established by Shor and Preskill [Phys. Rev. Lett. 85, 441 (2000)]] for a perfect source, indicating that the defects in the source are efficiently detected by the protocol.
authors.affiliation: CREST Research Team for Interacting Carrier Electronics, School of Advanced Sciences, The Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa, 240-0193, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Koashi
authors.forename: John
authors.initials: J
authors.lastname: Preskill