Precision gravity measurements with atom interferometry

This experimental work is devoted to perform accurate gravity measurements using atom interferometry. In the last two decades, atom interferometry has developed from an interesting demonstration of quantum physics into an important tool for precision measurements in fundamental physics as well as for practical applications in geodesy and inertial navigation. Essentially all such high precision atom interferometers are nowadays implemented using laser cooled atoms interacting with specially tailored pulses of light acting as beam splitters and mirrors for the matter-waves. In particular, the thesis is focused on the measurement of the Newtonian gravitational constant G through the use of a Rb cold atomic fountain. It relies on the simultaneous measurement of the accelerations of two vertically displaced, freely falling cold atomic samples, by means of Raman atom interferometry. The use of two displaced sensors allow a dramatic common mode phase noise suppression, so highly accurate gradiometric measurements are possible. Well-characterized source masses are placed close to the interferometers in two different positions and the relative phase shift is recorded. This removes the effects of all the fixed masses and makes the measurement doubly differential, both in time and space. A faithful simulation of the gravitational field of the source masses provides a phase shift as a function of G. This is compared to the acquired differential phase shift and a value of the gravitational constant is extracted. A study of the systematics leads to an aimed relative accuracy of the order of 10^-4.