  A complete physical approach to quantum information requires a robust
interface among flying qubits, long-lifetime memory and computational qubits.
Here we present a unified interface for microwave and optical photons,
potentially connecting engineerable quantum devices such as superconducting
qubits at long distances through optical photons. Our approach uses an
ultracold ensemble of atoms for two purposes: quantum memory and to transduce
excitations between the two frequency domains. Using coherent control
techniques, we examine an approach for converting and storing quantum
information between microwave photons in superconducting resonators, ensembles
of ultracold atoms, and optical photons as well as a method for transferring
information between two resonators.
