Preparation of a quantum state with one molecule at each site of an optical lattice

Ultracold gases in optical lattices are of great interest, because these systems bear great potential for applications in quantum simulations and quantum information processing, in particular when using particles with a long-range dipole - dipole interaction, such as polar molecules(1-5). Here we show the preparation of a quantum state with exactly one molecule at each site of an optical lattice. The molecules are produced from an atomic Mott insulator(6) with a density profile chosen such that the central region of the gas contains two atoms per lattice site. A Feshbach resonance is used to associate the atom pairs to molecules(7-14). The remaining atoms can be removed with blast light(13,15). The technique does not rely on the molecule-molecule interaction properties and is therefore applicable to many systems.