  By virtue of a silicon high-Q photonic crystal nanocavity, we propose and
examine theoretically interactions between a stationary electron spin qubit of
a semiconductor nanocrystal and a flying photon qubit. Firstly, we introduce,
derive and demonstrate for the first time the explicit conditions towards
realization of a spin-photon two-qubit phase gate, and propose these
interactions as a generalized quantum interface for quantum information
processing. Secondly, we examine novel single-spin-induced reflections as
direct evidence of intrinsic bare and dressed modes in our coupled
nanocrystal-cavity system. The excellent physical integration of this silicon
system provides tremendous potential for large-scale quantum information
processing.
