Feasibility Analysis for Quantum Key Distribution between a LEO Satellite and Earth

Terrestrial QKD channels can connect two links with a maximum distance of few hundred kilometres. In the case of fibre links, this is due to the signal attenuation in the fibre; in the case of free-space link the losses are due to atmospheric turbulence and absorption. Free-space optical terminals exploiting satellite-based relays are the only resource that can enable global scale quantum key distribution, since single photon propagation is for the main part in vacuum with no turbulence or absorption, and just a small part of the path is through the atmosphere. Several proof-of-principle experiments have been carried out recently: among these the feasibility of single-photon exchange between a satellite and an optical ground station was demonstrated in 2008.