Towards a measurement of the Casimir effect using a trapped ultra-cold atoms interferometer

At the micrometer scale, atom-surface interactions are dominated by the Casimir-Polder potential. This thesis is part of the development of the ForCa-G (Casimir Force and Short Range Gravitation) experiment where the measurement of short range forces (around the micrometer range) is performed using ⁸⁷Rb atoms cooled to temperatures of the order of a few hundred nano-kelvin and trapped in a vertical optical lattice in the vicinity of a dielectric surface.

In order to avoid contamination of this surface during the cooling steps, the atoms are prepared 30 cm below. We prove the efficiency of our transport method using Bloch oscillations, allowing both a satisfactory control of their final position without heating or excessive enlargement of the cloud radius in the vertical direction. An efficiency of up to 30% of the initial number of atoms has been measured after transport, which drops to 10% after recapture in the vertical lattice.

A sequence of stimulated Raman transitions then allows the spatial and coherent separation of the atomic wave packets on adjacent wells of the lattice and their recombination. This interferometer allows us to measure the energy difference between these wells, which is related to the different potentials seen by the atoms. A first measurement has been performed up to a distance of 1 µm from the surface, demonstrating the appearance of an attractive potential near the surface. However, initial analyses suggest that a parasitic electric field due to the adsorption of Rubidium atoms on the surface adds to the expected Casimir-Polder potential contribution.

cold atoms, atom interferometry, Casimir-Polder

Full document (FR) : HAL-04514581