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Phys Rev Lett. 2007 Jan 5;98(1):010504. Epub 2007 Jan 5.

Experimental demonstration of free-space decoy-state quantum key distribution over 144 km.

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Max-Planck-Institute for Quantum Optics, D-85748 Garching, Germany.


We report on the experimental implementation of a Bennett-Brassard 1984 (BB84) protocol type quantum key distribution over a 144 km free-space link using weak coherent laser pulses. Optimization of the link transmission was achieved with bidirectional active telescope tracking, and the security was ensured by employing decoy-state analysis. This enabled us to distribute a secure key at a rate of 12.8 bit/s at an attenuation of about 35 dB. Utilizing a simple transmitter setup and an optical ground station capable of tracking a spacecraft in low earth orbit, this outdoor experiment demonstrates the feasibility of global key distribution via satellites.

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