Darmstadt 2008 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 28: Poster Quanteninformation
Q 28.10: Poster
Tuesday, March 11, 2008, 16:30–19:00, Poster C2
Free Space Quantum Key Distribution with Coherent Polarization States — •Tim Bartley1, 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 — 2Department of Physics, Technical University of Denmark, Building 309, 2800 Kgs. Lyngby, Denmark
Quantum key distribution (QKD) is the process of establishing a secret shared key between two parties, traditionally named Alice and Bob. The security is based on the laws of quantum mechanics, in contrast to classical schemes, where security relies only on unproven mathematical assumptions.
In our free space QKD setup we encode the signal in coherent states which allow for convenient and fast state preparation and measurement. We utilize a pair of conjugate polarization variables (Stokes parameters) as signal carriers. This produces an excellent interference between signal and local oscillator without the need for stabilization. After the successful demonstration of this QKD scheme in the laboratory [1], we now present a proof-of-principle experiment under real free space conditions: the quantum states are transmitted over 100 m on the roof of our institute’s building. The use of a retro-reflector enables us to place Alice’s and Bob’s station on the same optical table. In the future, we plan to establish a QKD link between two distinct buildings 1.5 km apart.
[1] S. Lorenz et al., Phys. Rev. A 74, 042326 (2006).