Nouvelle génération de dispositif à microscope de grande ouverture pour le piégeage d’atomes individuels

摘要

This thesis presents the early work done on a new setup that we have developped for trapping single atoms in an optical tweezer using only one diffraction limited large numerical aperture aspheric lens. Together with an experimental optical measurement of a 1µm laser beam waist created by such an aspheric lens, we showed that the diffraction limited transverse field of the lens is about plus or minus 25 µm. The ability of this new setup to trap single atoms is demonstrated and some crucial parameters are then determined : survival time in the dark, heating rate, fluorescence light polarisation, oscillation frequencies. During this PhD, we did focus our attention especially on determining the energy distribution of the single trapped atoms. A release and recapture technique along with the spectroscopic study of the energy levels occupation helped us show a termal behavior of a succession of single atoms in an optical twezer. By using common laser cooling techniques associated with adiabatic down ramping cooling, we showed that a reduction by a factor 100 of the mean energy corresponding to a mean vibrationnal energy level of about 4 and a minimum temperature of 1,75 µK. Spatial manipulation of single atoms and qubits was also studied. Using a tip-tilt platform, a second trap is set on the experiment and the transfer from one trap to the other, as well as the displacement of one trap with help of the platform, are experimentally studied. Both the temperature of the atoms and the qubit lifetime are showed to be insensitive to these manipulations.