Universal photonic three-qubit quantum gates with two degrees of freedom assisted by charged quantum dots inside single-sided optical microcavities

Although universal quantum computation can be realized with two-qubit controlled-not (CNOT) gates and single-qubit rotations, it would be convenient to have resource-efficient and robust multiqubit quantum gates in practical quantum information processing. Here we present two new schemes to determinately implement three-qubit Toffoli gate and Fredkin gate on photon systems with two degrees of freedom (DOFs), assisted by charged quantum dots (QDs) inside single-sided optical microcavities. In contrast to the traditional Toffoli and Fredkin gates operating in photonic one DOF, the gates presented here with two DOFs can reduce the photon numbers required to implement the gate operations. Compared with the ones synthesized by CNOT and single-qubit gates, the present gates can reduce the complexity in experiment. Our schemes exploit the robust giant circular birefringence induced by a singleelectron spin in a QD-cavity system, which do not require photon indistinguishability or photon interference as demanded by other schemes using linear optics. Moreover, additional ancillary photons are not required in the schemes. We discuss the feasibility of our schemes, concluding that they can be realized with current or near-future technologies.