Berlin 2001 – scientific programme

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Q: Quantenoptik

Q 12: Quantum Information III

Q 12.3: Talk

Tuesday, April 3, 2001, 16:30–16:45, H 3010

Quantum Key Distribution — •Christine Silberhorn, Natalia Korolkova, and Gerd Leuchs — Zentrum für Moderne Optik, Universität Erlangen, Staudtstr. 7 / B2, 91058 Erlangen, Germany

Quantum key distribution is the most advanced technology in the field of quantum information processing. The conventional arrangements use dichotomic quantum systems to realize the secure information transfer. These discrete systems have the advantage to be loss insensitive in terms of security. However, the generation process for entangled photon pairs needed for quantum key distribution is spontaneous and therefore probabilistic. This limits the achievable data transmission rates. A new approach employs continuous variable systems [1], such as bright light fields, to obtain shorter key distribution times. In contrast to other continuous variable schemes our approach which makes use of an easy to handle source of EPR-entanglement does not use a predetermined key. Thus, the key generation process resemblance the one which has proven to be successful for dichotomic variables. The discretization of the continuous information stream into the bit-value key is implemented by the choice to measure either of the two conjugate variables. Thereby no resemblance information is needed to be sent through the quantum channel. The detection of the quantum correlations of the EPR-beams at the sender’s (Alice’s) station both ensures the security and serves to build the bit string.

[1] M. D. Reid, PRL 62, 062308, (2000); M. Hillery, PRA 61, 022309, (2000); T.C. Ralph, PRA 61, 010303

[2] Ch. Silberhorn et al, PRL, submitted (2000).