Time coding protocols for quantum key distribution
- THALES Research and Technology--France, Domaine de Corbeville, 91404 Orsay Cedex (France)
We propose quantum key distribution protocols based on coherent single-photon optical pulses with duration T and with minimum time-frequency uncertainty. The pulses are sent with possible delays (e.g., 0, T/2) that are used to code the information (e.g., bit 0, bit 1) and that are shorter than the pulse width. Therefore, the time detection of the photons may result in a ambiguity of the delay evaluation for a potential eavesdropper. The duration of the received pulses is controlled thanks to a contrast measurement using an interferometer. A quantum formalism is given, allowing us to model the transmission of the key and the consequences of a possible eavesdropping. Two protocols are proposed and discussed. The first one involves two states and is limited to channels with losses lower than 50%. The second one involves four states, which prevents the eavesdropper from exploiting the losses of the line. The security of each protocol is evaluated as a function of channel losses, quantum bit error rate, and contrast loss in the case of intercept-resend attacks. It is applied to situations where photocounters dark counts are the main limitation of the system. The resulting maximum propagation distance allowing secure communication is evaluated.
- OSTI ID:
- 20646342
- Journal Information:
- Physical Review. A, Vol. 70, Issue 4; Other Information: DOI: 10.1103/PhysRevA.70.042306; (c) 2004 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
Similar Records
Performance of a quantum key distribution protocol with dual-rail displaced photon states
Effect of finite detector efficiencies on the security evaluation of quantum key distribution