Satellite Based Quantum Communication

In collaboration with the Chinese Academy of Sciences, in particular with the group of Jian-Wei Pan from the University of Science and Technology of China, we are working on implementing single-photon and entanglement based quantum communication protocols between a Low-Earth-Orbit satellite and receiving stations on earth. The goal is to demonstrate secure quantum key distribution based on a decoy state protocol [1] intercontinentally between optical ground stations in Europe and China. Also, having an entangled photon source on a satellite will allow Bell tests [2] over distances at least an order of magnitude larger than at present.

The satellite – named after the Chinese philosopher “Mozi” – has been developed and constructed by our partners in China [3] and is currently being commissioned in-orbit. Our group has developed the required technology for optical ground stations in Europe and executed the necessary adaptations. Designated stations in Europe are the laser ranging station in Graz Lustbühel (Austria), ESA’s optical ground station in Tenerife (Spain) and IQOQI’s Hedy Lamarr Telescope in Vienna (Austria).

After successful commissioning measurements between the European ground stations and a satellite transmitter mock-up over horizontal free-space links, we are currently waiting for the first downlinks from Mozi. First in-orbit test of the pointing-acquisition-tracking system of the satellite could already be accomplished successfully.

The picture shows the beacon lasers during first commissioning tests of the bi-directional pointing-acquisition-tracking system of the Mozi satellite. The ground station fires a beacon laser with 671nm towards the satellite, while the satellite responses with a 532nm laser.

[1] V. Scarani, H. Bechmann-Pasquinucci, N. J. Cerf, M. Dušek, N. Lütkenhaus, M. Peev, The security of practical quantum key distributions, Rev. Mod. Phys. 81, 1301-1350 (2009).

[2] J. S. Bell, Speakable and Unspeakable in Quantum Mechanics, Cambridge University Press, New York (1987).

[3] H. Xin, Chinese Academy Takes Space Under Its Wing, Science 332 (6032), 904 (2011).