Experimentally testing decoherence due to gravity
Models of quantum systems on curved space-times lack sufficient experimental verification. Some speculative theories suggest that quantum properties, such as entanglement, may exhibit entirely different behavior to purely classical systems. By measuring this effect or lack thereof, we can test the hypotheses behind several such models. For instance, as predicted by Ralph and coworkers [T C Ralph, G J Milburn, and T Downes, Phys. Rev. A, 79(2):22121, 2009, T C Ralph and J Pienaar, New Journal of Physics, 16(8):85008, 2014], a bipartite entangled system could decohere if each particle traversed through a different gravitational field gradient. We propose to study this effect in a ground to space uplink scenario. We extend the above theoretical predictions of Ralph and coworkers and discuss the scientific consequences of detecting/failing to detect the predicted gravitational decoherence. We present a detailed mission design of the European Space Agency's (ESA) Space QUEST (Space - Quantum Entanglement Space Test) mission, and study the feasibility of the mission schema.
 Siddarth Koduru Joshi, Jacques Pienaar, Timothy C. Ralph, Luigi Cacciapuoti, Will McCutcheon, John Rarity, Dirk Giggenbach, Vadim Makarov, Ivette Fuentes, Thomas Scheidl, Erik Beckert, Mohamed Bourennane, David Edward Bruschi, Adan Cabello, Jose Capmany, José A. Carrasco, Alberto Carrasco-Casado, Eleni Diamanti, Miloslav Duusek, Dominique Elser, Angelo Gulinatti, Robert H. Hadfield, Thomas Jennewein, Rainer Kaltenbaek, Michael A. Krainak, Hoi-Kwong Lo, Christoph Marquardt, Gerard Milburn, Momtchil Peev, Andreas Poppe, Valerio Pruneri, Renato Renner, Christophe Salomon, Johannes Skaar, Nikolaos Solomos, Mario Stipčević, Juan P. Torres, Morio Toyoshima, Paolo Villoresi, Ian Walmsley, Gregor Weihs, Harald Weinfurter, Anton Zeilinger, Marek Żukowski, Rupert Ursin, arXiv:1703.08036 [quant-ph] (2017), submitted
Several feasibility studies have been performed under a FFG (national) and ESA contract already. Currently an industrial study lead by OHB is underway at the ESA level.