Conditional state generation in a dispersive atom-cavity field interaction with a continuous external pump field

The interaction of an atom with both a quantized cavity field and an external classical driving field, the fields being degenerate in frequency, is studied in the regime where the atom and fields are highly detuned. The atom interacts dispersively with the quantized field but the classical driving field gives rise to the creation or destruction of photons conditional on the state of the atom. We show how this interaction can be used to generate coherent states of the cavity field and various forms of superpositions of macroscopically distinct states. This method is in contrast to the usual method used in microwave cavity QED of injecting a coherent state into a cavity via a waveguide attached to a klystron and where subsequently Schroedinger cat states may be generated by manipulating the field with injected atoms. The method proposed here could possibly be used in the case of an optical cavity. Further, we show that coherent states may be generated in the steady state from the competition between the driven dispersion interaction and dissipative single-photon losses, a form of optical balance