Berlin 2005 – wissenschaftliches Programm
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Q: Quantenoptik und Photonik
Q 33: Quantenkommunikation II
Q 33.3: Vortrag
Dienstag, 8. März 2005, 11:15–11:30, HU Audimax
Detecting quantum correlations in quantum key distribution protocols — •O. Gühne1, M. Curty2, M. Lewenstein3, and N. Lütkenhaus2 — 1Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, A-6020 Innsbruck — 2Quantum Information Theory Group, Institut für Theoretische Physik I, and Max-Planck Research Group, Institute of Optics, Information and Photonics, Universität Erlangen-Nürnberg, Staudtstr. 7/B2, D-91058 Erlangen — 3Institut für Theoretische Physik, Universität Hannover, Appelstr. 2, D-30167 Hannover
Quantum key distribution (QKD) enables secure communication between two parties. For practical implementations it is important to know under which conditions a given QKD protocol is secure or not. It has been shown that a necessary precondition for secure QKD is that sender and receiver can prove the presence of entanglement in the quantum state that is effectively distributed between them. In this contribution, we demonstrate that entanglement witnesses (EW) are powerful tools in order to deliver this entanglement proof. The class of EWs that can be constructed from the available measurements results can be used to provide a necessary and sufficient condition for the existence of quantum correlations. First, we present the set of optimal EWs for two entanglement based (EB) schemes, the 6-state and the 4-state EB protocols. Then, we analyze prepare&measure (P&M) schemes. For this, we investigate the 4-state and the 2-state P&M schemes. For each of these protocols we obtain a reduced set of EWs, yielding a necessary and sufficient condition for the existence of quantum correlations.