We trap neutral Cs atoms in a two-dimensional optical lattice and cool them close to the zero-point motion by resolved-sideband Raman cooling. Sideband cooling occurs via transitions between the vibrational manifolds associated with a pair of magnetic sublevels and the required Raman coupling is provided by the lattice potential itself. We obtain mean vibrational excitations nx ª ny ª 0.01, corrensponding to a population ~98% in the vibrational ground state. Atoms in the ground state of an optical lattice provide a new system in which to explore quantum state control and subrecoil laser cooling.
Physical Review Letters 80, 4149 (1998).