  The single photon occupation of a localized field mode within an engineered
network of defects in a photonic band-gap (PBG) material is proposed as a unit
of quantum information (qubit). Qubit operations are mediated by
optically-excited atoms interacting with these localized states of light as the
atoms traverse the connected void network of the PBG structure. We describe
conditions under which this system can have independent qubits with
controllable interactions and very low decoherence, as required for quantum
computation.
