Coupled quantum electrodynamics in photonic crystal nanocavities

We show that a scalable photonic crystal nanocavity array, in which single embedded quantum dots are coherently interacting, can perform as an universal single-operation quantum gate. In a passive system, the optical analogue of electromagnetically-induced-transparency is observed. The presence of a single two-level system in the array dramatically controls the spectral lineshapes. When each cavity couples with a two-level system, our scheme achieves two-qubit gate operations with high fidelity and low photon loss, even in the bad cavity limit and with non-ideal detuning and decoherence.