QUIE2T Quantum Information Entanglement-Enabled Technologies

Physical approaches and perspectives

The European Space Agency ESA has supported various studies in the field of quantum physics and quantum information science in space for several years [1]. Quantum Communication has now reached a sufficient maturity level to allow for space qualification of the relevant components. The mission proposal Space-QUEST (Quantum Entanglement for Space Experiments) has been submitted to the European Life and Physical Sciences in Space Program and is now in the planning phase with ESA. The objective is to perform space-to-ground quantum communication tests from the International Space Station (ISS) as a first proof-of-principle demonstration of quantum communication using space-based platforms. The launch plan is compatible with 2014.

European groups working in this field include: A. Zeilinger (Vienna, AT), H. Weinfurter (Munich, D), J. Rarity (Bristol, UK), C. Barbieri & P. Villoresi (Padova, I), S. Cova (Milan, I), I. Walmsley (Oxford, UK), R. Renner (Zurich, CH), P. Martoloni (Rome, I), M. Dušek (Olomouc, CZ), M. Bourennane (Stockholm, SW) as well as an international team of 40 scientist on the Space-QUEST Topical Team as a scientific advisory committee.

State of the art

Many of the recent advances have focused on collaborative work taking place in the Canary Islands by several leading European groups. The key results range from highly practical aspects such as the implementation of detection synchronisation based on the ultra-stable clocks provided by the global positioning system (GPS), an active low bandwidth (tip-tilt) beam control for a free-space long-distance quantum communication link and more generally interfacing quantum communications with existing hardware for earth-based optical satellite communication: (1) the Optical Ground Station (OGS) of the European Space Agency ESA on the Canary Island Tenerife acted as the receiver station for a free-space long-distance quantum communication link [2]; (2) the Matera Laser Ranging Observatory (MLRO) in Southern Italy served as transceiver station for faint-pulse exchange with a low-earth orbit retro-reflecting satellite at a perigree of 1485 km [3]. Other important steps included: the demonstration of a continuous 24h free-space QKD link in the Vienna SECOQC network over 200 m; a design study for a satellite-based entangled photon source has been completed in collaboration with the European Space Agency ESA; and the quantum key distribution over 144 km (between the Canary Islands of La Palma and Tenerife) has been extended to entanglement-based distribution.

Challenges

The European groups have taken a leading role in this endeavour, although the current Space-Quest consortium also consists of groups in Australia, Japan and the US while Japan has independent plans for a QKD launch in 2013. The key challenges are:

• Development of compact & robust high photon flux sources – depending on the architecture and protocol, the systems must operate in short burst when satellites are in view;
• Develop novel CV protocols that could be immune to the high loss that exist in these links;
• Study complex spatial mode structures as decoherence-free states in free space channels, that don’t suffer by turbulences / diffraction (discrete and CV);
• Robust systems that can for example withstand launch g-forces;
• Space certification for component technologies.

[1] J. Armengol et al., Acta Astronautica 63, 165 (2008); R. Ursin et al., Europhysics News, 40, 26 (2009)
[2] R. Ursin, et. al., Nature Physics, 3, 481 (2007); A. Fedrizzi, et.al., Nature Physics. 5, 389 - 392 (2009); T. Scheidl et al., arXiv:0811.3129 (2008)
[3] P Villoresi et al., New J. Phys., 10 033038 (2008)