title: Large-alphabet quantum key distribution using energy-time entangled bipartite States.
abstract: We present a protocol for large-alphabet quantum key distribution (QKD) using energy-time entangled biphotons. Binned, high-resolution timing measurements are used to generate a large-alphabet key with over 10 bits of information per photon pair, albeit with large noise. QKD with 5% bit error rate is demonstrated with 4 bits of information per photon pair, where the security of the quantum channel is determined by the visibility of Franson interference fringes. The protocol is easily generalizable to even larger alphabets, and utilizes energy-time entanglement which is robust to transmission over large distances in fiber.
authors.affiliation: Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA.
authors.forename: Irfan
authors.initials: I
authors.lastname: Ali-Khan
authors.forename: Curtis J
authors.initials: CJ
authors.lastname: Broadbent
authors.forename: John C
authors.initials: JC
authors.lastname: Howell