Quantum electrodynamics of excitons in a cavity is shown to be relevant to quantum operations. We present a theory of an integrable solid-state quantum controlled-phase gate for generating entanglement of two photons using a coupled nanodot-microcavity-fiber structure. A conditional phase shift of O(pi/10) is calculated to be the consequence of the giant optical nonlinearity keyed by the excitons in the cavities. Structural design and active control, such as electromagnetically induced transparency and pulse shaping, optimize the quantum efficiency of the gate operation.