  We propose a two-qubit quantum logic gate between a superconducting atom and
a propagating microwave photon. The atomic qubit is encoded on its lowest two
levels and the photonic qubit is encoded on its carrier frequencies. The gate
operation completes deterministically upon reflection of a photon, and various
two-qubit gates (SWAP, $\sqrt{\rm SWAP}$, and Identity) are realized through
{\it in situ} control of the drive field. The proposed gate is applicable to
construction of a network of superconducting atoms, which enables gate
operations between non-neighboring atoms.

Quantum Physics;Superconductivity