Darmstadt 2008 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 28: Poster Quanteninformation
Q 28.9: Poster
Tuesday, March 11, 2008, 16:30–19:00, Poster C2
Fiber based Quantum Cryptography with Continuous Variables — •Josef Fürst1, Carlos H. Wiechers M.1,3, Dominique Elser1, Christoffer Wittmann1, Ulrik L. Andersen1,2, and Gerd Leuchs1 — 1Institut für Optik, Information und Photonik, Max-Planck-Forschungsgruppe, Universität Erlangen-Nürnberg, Günther-Scharowsky-Str. 1 / Bau 24, 91058 Erlangen, Germany — 2Department of Physics, Technical University of Denmark, Building 309, 2800 Kgs. Lyngby, Denmark — 3Instituto de Física de la Universidad de Guanajuato, Lomas del Bosque 103, 37150 León, Guanajuato, Mexico
Quantum Key Distribution (QKD) offers a secure method of sharing a secret key between two parties, commonly called Alice and Bob. In general, there are two different kinds of QKD protocols either with discrete variables or with continuous variables. We implement a continuous variable protocol with binary encoded coherent states, which offers convenient state preparation and measurement. No entanglement source is present in our prepare and measure scheme. However, the nonorthogonality of the signal states, encoded by discrete phase and amplitude modulation, leads to effective entanglement [1]. The encoded states (ES) and the Local Oscillator (LO) are sent from Alice to Bob via a single optical fiber using time multiplexing. Thereby, scattering from the LO into the ES, which generates noise, is prevented. Subsequently, we measure both conjugate quadratures of the ES by homodyne detection and generate the raw key using postselection.
[1] S. Lorenz et al., Phys. Rev. A 74, 042326 (2006)