Implementations of two-photon four-qubit Toffoli and Fredkin gates assisted by nitrogen-vacancy centers

摘要

It is desirable to implement an efficient quantum information processdemanding fewer quantum resources. We designed two compact quantum circuits fordeterminately implementing four-qubit Toffoli and Fredkin gates onsingle-photon systems in both the polarization and spatial degrees of freedom(DoFs) via diamond nitrogen-vacancy (NV) centers in resonators. The gates areheralded by the electron spins associated with the diamond NV centers. Incontrast to the ones with one DoF, our implementations reduce the quantumresource and are robust against the decoherence. Evaluations of fidelities andefficiencies of our gates show that our schemes may be implemented with currenttechnology.