EU: Long-Lived Quantum Memories for Space-Based Applications (QSPACE)

Quantum experiments in space open up numerous interesting technological and scientific possibilities in the last years. Long-distance quantum communication (QC) is one of the first applications that would benefit from these advances as quantum information can be transferred over very long distances by satellites. However, this range is limited by the line-of sight distance which limits the direct transmission of quantum information to around few thousand kilometres. One solution to reach true global distances while relaxing the security assumptions used in satellite QC is to equip satellites with quantum memories (QMs). This would allow the implementation of satellite-based quantum repeater networks that could potentially cover global distances and increase the secret key rates by synchronising otherwise probabilistic detection events. On the other hand, scientifically, the possibility of observing gravitational effects on quantum systems has the promise of bringing new perspectives into the search of a quantum theory of gravitation. In this regard, research into long-lived entanglement of quantum matter systems in curved space time could yield new physical insights. Along these lines we propose to develop a space-compatible, small-footprint laser-cooled quantum memory with storage times in the order of seconds. Our preliminary work suggests that such a system could beat the memory-less quantum communication schemes with realistic memory performances.