Quantum mechanics for space applications

This paper is an introduction to the following articles in the scope of the Quantum Mechanic for Space Study initiated by ESA and lead by ONERA. The context of Quantum Mechanics for Space is summarised, and fields under development concerned are briefly introduced. On one hand, technological applications in space of quantum mechanics are explored and on the other hand some test of quantum mechanics are outlined. We also give a brief presentation of the Opto-electronics Section at the European Space Agency and on the technology development activities it carries out, with particular emphasis on those activities related to the topics of interest of the Quantum Mechanics in Space workshop. As an example, a summary of two ESA studies on gravity gradiometry and their relevance to the field of atomic interferometry is given. In the light of the scientific requirements, derived for both Earth Observation and Planetology for future space missions, atom interferometry shows promise and may be at an advantage with respect to currently available accelerometer and inertial sensor systems. 1 Quantum Mechanics and space Quantum mechanics (QM) is a theory that had been developed at the beginning of the previous century. One of ⋆ http://qm-space.onera.fr the main idea in this theory is the wave particle duality : particles, for example electrons, can behave like waves and waves, for example light, can be seen like particles. QM was able to explain many phenomena ranging from the black body radiation to atomic spectra and is now a well establish theory that described the behaviour of the matter at the microscopic scale. However, some aspects of QM theory remain unsolved like the problem of the measurement or the unification with general relativity or some phenomena are not yet fully understood like for example the superconductivity and there is thus still an important research effort in QM both theoretically and experimentally. Although rather new and fundamental, QM already extends its interest beyond the academic research and has already lead to a wide range of technologies like the laser, the transistor or the atomic clocks. Nowadays, there is even a boost in QM based technologies for example with quantum information. Many of these technologies like quantum detector or atomic clocks may find their ultimate use and performances when applied in space mission since space and in particular microgravity can provide a very attractive environment. In space, the microgravity allows to obtain long interaction time and therefore to make extremely precise measurement, and it also provides a quiet and isolated environment where a better understanding of QM can be acheived such as for example a study of quantum decoherence. QM and space have thus an ‘intimate’ relationship. One can use space to study QM and one can use QM based technology for space mission. In order to identify the most promising field of QM in space, ESA initiated the QM for space study. This project has been lead by ONERA and was made with the co-operation of famous research institute or laboratories: IOTA (Orsay, France), SYRTE (Paris, France), IQO (Hanover, Germany), and University of Strathclyde(UK). A roundtable has been organised in the frame of the project. This event has outlined the developments in QM based technologies for space applications and tests by bringing together European experts in the relevant theoretical and technological domains. It has been the opportunity to build together new ideas and perspectives for applications of QM, and to establish a link between ESA and this scientific community. Based on several criteria like the needs resulting from space missions, the scientific maturity or the global interest, the QM for space study selected five relevant fields :