title: Quantum cryptography using entangled photons in energy-time bell states
abstract: We present a setup for quantum cryptography based on photon pairs in energy-time Bell states and show its feasibility in a laboratory experiment. Our scheme combines the advantages of using photon pairs instead of faint laser pulses and the possibility to preserve energy-time entanglement over long distances. Moreover, using four-dimensional energy-time states, no fast random change of bases is required in our setup: Nature itself decides whether to measure in the energy or in the time base, thus rendering eavesdropper attacks based on "photon number splitting" less efficient.
authors.affiliation: Group of Applied Physics, University of Geneva, CH-1211, Geneva 4, Switzerland.
authors.initials: W
authors.lastname: Tittel
authors.initials: J
authors.lastname: Brendel
authors.initials: H
authors.lastname: Zbinden
authors.initials: N
authors.lastname: Gisin