A free-space test range for global quantum key distribution feasibility studies

Summary form only given. Quantum cryptographic systems employ secret keys exchanged between two parties in the form of a stream of polarisation- or phase-encoded single photons. Under ideal conditions the absolute security of the quantum key is guaranteed by the laws of quantum physics, since any attempt at eavesdropping will introduce gross bit errors which will be quickly detected by the legitimate parties to the key exchange. Secure quantum key distribution (QKD) it currently limited to distances of several tens of kilometres. It has been suggested that key distribution over global distances will require the use of free-space optical intersatellite (O-ISL) and ground to satellite links. Free-space terrestrial paths provide a natural propagation medium in which to investigate the viability of ground to satellite single photon QKD links. We describe the use of an optical free-space range based on a satellite laser ranging observatory instrumented for this purpose.