München 2004 – scientific programme
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Q: Quantenoptik und Photonik
Q 22: Poster Quanteninformation, -kommunikation und -computer
Q 22.14: Poster
Tuesday, March 23, 2004, 14:00–16:00, Schellingstr. 3
Efficiency of quantum key distribution protocols based on coherent states, homodyne detection and post selection — •Matthias Heid1,2 and Norbert Lütkenhaus1,2 — 1Institut für Theoretische Physik I, Universität Erlangen-Nürnberg — 2Institut für Optik, Information und Photonik (Max-Planck Forschungsgruppe), Universität Erlangen-Nürnberg
Quantum key distribution (QKD) protocols can be implemented with many different signal sources and detection devices. The usual implementation with weak coherent pulses and single-photon detection gives a key rate G that scales with the single-photon transmission as G ≈ η2. If we use instead a single-photon source, the rate will scale as G ≈ η. However, single photon sources are still comparatively difficult to implement. An alternative approach uses coherent states together with variations of a homodyne detection [1]. The aim is to obtain high repetition rates to boost the key rate. We analyse the expected key rates for various schemes based on postselection procedures [2,3] and four coherent signal states [2]. For a practical implementation of a QKD scheme we also take imperfect detectors into account.
[1] F. Grosshans and P. Grangier, Phys. Rev. Lett. Vol 88, 057902 (2002).
[2] T. Hirano and R. Namiki, Phys. Rev A Vol 67, 022308 (2003).
[3] CH. Silberhorn, T.C. Ralph, N. Lütkenhaus, G. Leuchs, Phys. Rev. Lett., Vol. 89, 167901 (2002).