Preparation of microwave single-photon states via a superconducting circuit

We propose a scheme for preparing a stationary microwave single-photon state of a transmission line resonator via off-resonant interaction with a single superconducting Cooper-pair Box (CPB). It is shown that with the help of an auxiliary microwave field, single-photon state can be persistently produced with high efficiency by using the CPB and cavity loss. The scheme is feasible with the current experimental technology and can be extended to prepare a multiphoton Fock state in a transmission line cavity.