The general frame of the PhD project is the application of atom interferometry techniques to the measurement of the Earth gravity field from satellites, which is under consideration at space agencies in France, Europe and US. Atom interferometers possess remarkable properties, which make them ideal sensors for the measurement of inertial forces: they provide accurate measurements and do not suffer from bias drifts, so that their operation do not require calibration. These features give to these sensors long term stabilities better than classical sensors.
If the space environment will allow for a drastic increase in the duration of the interferometer with respect to on ground operation (where this time is typically limited to a fraction of a second due to the free fall of the atoms) and thus for reaching much improved intrinsic sensitivities, it is difficult to reach, with the conventional interferometer geometry based on the use of two photon transition beamsplitters, performances in terms of gradiometry largely improved with respect to the state of the art sensors, such as the electrostactic gradiometers of the GOCE mission.
We propose here to study of new interferometer geometries which will allow to reach performances on the measurement of gravity gradients better than the mE/Hz1/2 in space, thanks to the increase in the efficiency of the beamsplitter of the interferometer. Such sensitivities would allow to improve the resolution on the meaurement of gravity gradients, in particular for Fourier frequencies below 10 mHz
Different techniques have been developped over the last years, which allow to reach transfer of several tens of photons, instead of two, or four, obtained classically with Raman transitions. Yet, these new tools do not possess the same level of maturity as the former. The aim of this thesis is to evaluate the benefit of these new techniques to atom interferometry, via the study of a laboratory gradiometer instrument, developed with the support of CNES with an ongoing R&T study. This instrument combines the use of high power laser sources based on frequency doubled telecom laser to realize the laser beams of the interferometer, and of ultracold atom sources produced on atom chips using evaporative cooling techniques. These sources have the advantage of being denser and colder, which will allow exploiting the full benefit of powerful laser, first by using laser beams of reduced sizes, which will increase the intensity on the atoms, and second because the colder the atoms, the better the efficiency of multiphotonic transitions. The thesis will consist on the implementation of these new tools on the SYRTE gradiometer, and on the detailed study of the performances obtained, in order to extrapolate these performances to the space environment.
Good training in general physics
Specialty Master Atomic Physics / Optics