Stuttgart 2012 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 24: Quanteninformation: Repeater und Speicher

Q 24.7: Talk

Tuesday, March 13, 2012, 12:15–12:30, V7.02

Demonstration of QKD with a compact and mobile single photon source based on defect centers in diamond — Matthias Leifgen, Tim Schröder, •Robert Riemann, Friedemann Gädeke, and Oliver Benson — HU Berlin, Inst. für Physik, AG Nano-Optik, Newtonstr. 15, 12489 Berlin

Quantum key distribution (QKD) is an absolute secure way of distributing keys for secure data encryption. Experimental realizations have become much more mature recently. Mostly, attenuated laser pulses are used as light source rather than true single photons, which would be the obvious choice theoretically. This is due to various difficulties of producing single photons efficiently. Single photons, if produced efficiently and at a high rate, would be the light source of choice for QKD. Furthermore, they provide inherent security from the so-called photon number splitting attack of an eavesdropper. Here we demonstrate QKD with single photons from a single nitrogen-vacancy center inside a nanodiamond. The overall efficiency of the single photon source we use, taking only detected photons per excitation pulse into consideration, is about 2% and relatively high photon rates can be achieved. This efficiency is comparable to attenuated laser pulses (without decoy states), which have to be attenuated strongly to provide security. We implement the BB84 protocol and use the polarization of the photons for encryption. The setup is designed to account for the relatively broadband single photons (FWHM 100nm) generated by the NV centers. The compact and mobile single photon source is ready to use and can easily be integrated into the QKD setup.