  We present an approach to achieve efficient single-photon frequency
conversion in the microwave domain based on coherent control in superconducting
quantum circuits, which consist of a driven artificial atom coupled to a
semi-infinite transmission line. Using the full quantum-mechanical method, we
analyze the single-photon scattering process in this system and find that
single-photon frequency up- or down-conversion with efficiency close to unity
can be achieved by adjusting the parameters of the control field applied to the
artificial atom. We further show that our approach is experimentally feasible
in currently available superconducting flux qubit circuits.
