Quectonewton Local Force Sensor

We report on the realization of a quantum sensor based on trapped atom\ninterferometry in an optical lattice for the measurement of atom-surface\ninteractions, with sub-micrometer-level control of the mean atom-surface\nseparation distance. The force sensor reaches a short-term sensitivity of 3.4 x\n10 --28 N at 1 s and a long-term stability of 4 qN (4 x 10 --30 N). We perform\nforce measurements in the 0-300 $\\mu$m range, and despite significant stray\nforces caused by adsorbed atoms on the surface, we obtain evidence of the\nCasimir-Polder force. Short-range forces are one of the many frontiers of\nmodern physics [1, 2]. In the submillimeter scales, quantum electrodynamics\n(QED) interactions are dominant, and give rise in the case of atom-surface\ninteractions to the Casimir-Polder force [3]. Since the first highlight of this\nforce [4], several different methods [5] have been able to bring out\nCasimir-Polder forces, notably by measuring the transmission of an atomic beam\nthrough a micronsized cavity [6], diffracting matter waves on a surface [7] or\nperforming spectroscopy in vapor cells [8, 9]. However these approaches have\nstruggled to achieve the high measurement sensitivity required to detect the\nvery weak forces involved all while maintaining a good understanding of the\nsetup geometry, particularly the distance separating atoms from the surface.\nFew experiments have achieved measuring Casimir-Polder forces while controlling\ndirectly the atom-surface distance. In the range from tens to hundreds of\nnanometers, the Casimir-Polder potential was measured directly by reflecting\nthe atoms on an evanescent field [10, 11]. In\n