Quantum sensor for atom-surface interactions below 10 mu m

We report the realization of a quantum device for force sensing at the micrometric scale. We trap an ultracold Sr-88 atomic cloud with a one-dimensional (1D) optical lattice; then we place the atomic sample close to a test surface using the same optical lattice as an elevator. We demonstrate precise positioning of the sample at the micrometer scale. By observing the Bloch oscillations of atoms into the 1D optical standing wave, we are able to measure the total force on the atoms along the lattice axis, with a spatial resolution of few micrometers. We also demonstrate a technique for transverse displacement of the atoms, allowing us to perform measurements near either transparent or reflective test surfaces. In order to reduce the minimum distance from the surface, we compress the longitudinal size of the atomic sample by means of an optical tweezer. This system is suited for studies of atom-surface interaction at short distance, such as measurement of the Casimir force and the search for possible non-Newtonian gravity effects.