Energy distribution and cooling of a single atom in an optical tweezer

Abstract

We investigate experimentally the energy distribution of a single $^{87}\mathrm{Rb}$ atom trapped in a strongly focused dipole trap under various cooling regimes. Using two different methods to measure the mean energy of the atom, we show that the energy distribution of the radiatively cooled atom is close to thermal. We then demonstrate how to reduce the energy of the single atom, first by adiabatic cooling, and then by truncating the Boltzmann distribution of the single atom. This provides a nondeterministic way to prepare atoms at low micro-K temperatures, close to the ground state of the trapping potential.