Abstract
We used the Toulouse atom interferometer to study how Van der Waals (VdW) interactions between atoms and surfaces cause velocity-dependent phase shifts for atomic de Broglie waves. By introducing a thin nano-grating in one branch of this interferometer, we observed a phase shift that depends on velocity to the power −0.49. This dispersion serves to measure both the strength and the position dependence of the atom-surface potential in the range from 5 to 10 nm from the surface, and it can also set new limits on non-Newtonian gravity in the 2 nm range.