Heralded universal quantum computing on electron spins in diamond nitrogen-vacancy centers assisted by low-Q microtoroidal resonators

Heralded universal quantum gates can largely decrease the quantum resource consumed in the integration of a multiqubit quantum circuit. Here, we present a scheme for heralded universal quantum computing, including the construction of the CNOT gate, Fredkin gate, and Toffoli gate on the electron spins in diamond nitrogen-vacancy (NV) centers assisted by low- Q microtoroidal resonators. These quantum gates can achieve unity fidelity, as the infidelity induced by the imperfect input-output process is transferred into photon loss. The dicks on different single-photon detectors can either herald the success of the quantum gates or instruct an immediate recycling procedure, even without reinitializing the NV centers. Besides the heralding, this scheme is also more realistic, observing that the non-monochromatic auxiliary photon and the inhomogeneous NV centers have no adverse impact on fidelity. The high fidelity and efficiency with experimental parameters show that the scheme is feasible with current technology. (C) 2020 Optical Society of America