Sensitive gravity-gradiometry with atom interferometry: progress towards an improved determination of the gravitational constant

We present here the current status of our high-sensitivity gravity-gradiometer based on atom interferometry. In our apparatus, two clouds of laser-cooled rubidium atoms are launched in a fountain configuration and simultaneously interrogated by a Raman-pulse interferometry sequence. The system has recently been upgraded and its stability re-evaluated. We also discuss the recent progress of the experiment towards a precise determination of the Newtonian gravitational constant G. The signal-to-noise ratio and the long-term stability of the gravity gradiometer demonstrated interesting perspectives for pushing the G measurement precision below the 100 ppm level.