Berlin 2005 – scientific programme
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Q: Quantenoptik und Photonik
Q 3: Poster Quanteninformation, -kommunikation und Quantencomputer
Q 3.24: Poster
Friday, March 4, 2005, 11:00–12:30, Poster HU
Performance of quantum key distribution protocols based on coherent states and homodyne detection under realistic conditions — •Matthias Heid1,2 and Norbert Lütkenhaus1,2 — 1Institut für theoretische Physik I, Universität Erlangen-Nürnberg — 2Institut für Optik, Information und Photonik (Max-Planck Forschergruppe), Universität Erlangen-Nürnberg
Quantum key distribution (QKD) protocols can be implemented with many different signal sources and detection devices. In practice, QKD with single photon sources and single photon counting suffers from the fact that the source is experimentally still hard to implement. Weak coherent pulses are therefore often used instead. An alternative approach uses coherent states together with variations of homodyne detection. The aim here is to use a detection setup wich can operate at high repetion rates to boost the secret key rate.
In a practical implementation however, one has also to take into account that the error correction procedure used by the honest parties to correct for errors in their data never work at the ideal theoretical limit. This reduces the secret key rate.
We analyse the influence of this effect on the expected secret key rates for various schemes based on postselection [1] or reverse reconcilation [2]. As signals we assume a discrete distribution of coherent signal states and take imperfect detectors into account.
[1] Ch. Silberhorn, T. C. Ralph, N. Lütkenhaus, G. Leuchs, Phys. Rev. Lett., Vol. 89, 167901 (2002)
[2] F. Grosshans et al., Nature, Vol. 421, 238 (2003)