Berlin 2005 – scientific programme

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Q: Quantenoptik und Photonik

Q 11: Quantenkommunikation I

Q 11.6: Talk

Saturday, March 5, 2005, 09:45–10:00, HU Audimax

Entanglement detection in QKD — •Tobias Moroder, Marcos Curty, and Norbert Lütkenhaus — University Erlangen-Nuremberg, Institute of Theoretical Physics I, Quantum Information Theory Group

It is a necessary condition for secure quantum key distribution that the correlations generated in the corresponding experiment exhibit quantum correlations [1]. The search for quantum correlations can be phrased as a search for entanglement. The tools are restricted by the actually performed measurements and the set-up and, typically, does not give tomographically complete information that would allow reconstructing the bipartite density matrix.

An appropriate tool to verify this entanglement are entanglement witnesses that are restricted to some classes linked to the set-up. In this presentation we investiate the time coding protocol by Debuisschert and Bocher [2]. We utilize semidefinite programming to search for quantum correlations. This allows us to compare the limitations of this protocol with that of other protocols. Additionally, we can derive simple upper bounds on the secret key rates once quantum correlations have been verified.

[1] M. Curty, M. Lewenstein, N. Lütkenhaus, Entanglement as precondition for secure quantum key distribution, Phys. Rev. Lett. 92, 217903 (2004)

[2] T. Debuisschert, W. Boucher, Time coding protocols for quantum key distribution, Phys. Rev. A 70, 042306 (2004)