The Quantum Measurement of Gravity for Geodesists and Geophysicists

During the past 30 years a great advancement in low-energy physics, particularly interactions of atoms with the electromagnetic field, has been achieved. Quoting the Nobel Prize talk of C. Cohen-Tannoudji, we can say that the development of electronics and laser techniques has allowed to implement a fine manipulation of atoms with photons. In this way, following the theory already worked out in the 50s, physicists have learnt how to cool a sample of atoms at the level of the microkelvin ðlk) and, nowadays, even in the range of the nanokelvin (nk). A wealth of important applications has sprung out from this ability of manipulating large samples (N of the order of 10 to the seventh) of cold atoms; among them we mention, regarding the improvement of atomic clocks, the creation of atomic gyroscopes and of atomic gravity meters. This last item is obviously of great interest to geodesists and geophysicists, particularly for potential applications to space geodesy.