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Q: Fachverband Quantenoptik und Photonik

Q 56: Poster IV

Q 56.42: Poster

Thursday, March 5, 2009, 16:30–19:00, VMP 9 Poster

Witnessing Effective Entanglement over 20km of Optical Fibre — Christoffer Wittmann¹, •Josef Fürst¹, Carlos Wiechers^1,2, Dominique Elser¹, Hauke Häseler^1,3, Norbert Lütkenhaus^1,3, and Gerd Leuchs¹ — ¹Max-Planck-Institut für die Physik des Lichts , Günther-Scharowsky-Str. 1 / Bau 24, 91058 Erlangen, Germany — ²Instituto de Física de la Universidad de Guanajuato — ³Institute for Quantum Computing, University of Waterloo

We report first results on the experimental demonstration of effective entanglement in a prepare-and-measure type of quantum key distribution protocol. Following previous experiments [1], we send coherent states over a quantum channel and use heterodyne measurements to characterize the transmitted quantum states, reconstructing directly their Q function. In the new experiment, the quadrature encoded quantum states are sent through a 20km fibre channel. Hereby we increased the length of the quantum channel compared to the previous experiment. Furthermore, we monitor the local oscillator power as demanded in [2].

[1] S. Lorenz, J. Rigas, M. Heid, U.L. Andersen, N. Lütkenhaus and G. Leuchs, Phys. Rev. A 74, 042326 (2006), [2] H. Häseler, T. Moroder and N. Lütkenhaus, Phys. Rev. A 77, 032303 (2008)