Optically controlled quantum gates for three spin qubits in quantum dot–microcavity coupled systems

We investigate theoretically the possibility of achieving feasible solid-state quantum computing by compactly constructing a set of two or three quantum gates on stationary electron spin qubits, including the controlled NOT gate, Toffoli gate and Fredkin gate. In our schemes, both of the target qubits and control qubits are all encoded on the confined electron spins in quantum dots embedded in optical microcavities with two partially reflective mirrors. In this paper, the schemes are based on spin selective photon reflection from the microcavity and are achieved in deterministic ways by the sequential detection of the auxiliary photons. The feasibilities of the proposed schemes are estimated by high average fidelities of the gates which are achievable in both the weak coupling and the strong coupling regimes. Under the present technology, our proposed schemes are feasible, opening the promising perspectives for constructing a solid-state quantum computation and quantum information processing.