  We present an in-situ study of an optical lattice with tunneling and single
lattice site resolution. This system provides an important step for realizing a
quantum computer. The real-space images show the fluctuations of the atom
number in each site. The sub-Poissonian distribution results from the approach
to the Mott insulator state, combined with the dynamics of density-dependent
losses, which result from the high densities of optical lattice experiments.
These losses are clear from the shape of the lattice profile. Furthermore, we
find that the lattice is not in the ground state despite the momentum
distribution which shows the reciprocal lattice. These effects may well be
relevant for other optical lattice experiments, past and future. The lattice
beams are derived from a microlens array, resulting in lattice beams which are
perfectly stable relative to one another.
