  Cavity-optomechanics is an ideal platform for the generation non-Gaussian
quantum states due to the anharmonic interaction between the light field and
the mechanical oscillator; but exactly this interaction also impedes the
preparation in pure states of the light field. In this paper we derive a
driving protocol that helps to exploit the anharmonic interaction for state
preparation, and that ensures that the state of the light field remains
close-to-pure. This shall enable the deterministic preparation of photon Fock
states or coherent superpositions thereof.
