  We calculate single atom heating rates in a far detuned optical lattice, in
connection with recent experiments. We first derive a master equation,
including a realistic atomic internal structure and a quantum treatment of the
atomic motion in the lattice. The experimental feature that optical lattices
are obtained by superimposing laser standing waves of different frequencies is
also included, which leads to a micromotional correction to the light shift
that we evaluate. We then calculate, and compare to experimental results, two
heating rates, the "total" heating rate (corresponding to the increase of the
total mechanical energy of the atom in the lattice), and the ground bande
heating rate (corresponding to the increase of energy within the ground energy
band of the lattice).
