Scalable multi-qubit quantum gates in quantum networks based on the microtoroidal-resonator-mediated nitrogen-vacancy centers in diamond

In the paper, we present schemes for implementing multi-qubit quantum gates in quantum networks based on the nitrogen-vacancy (NV) centers in diamond. In our schemes, NV centers coupled to the whispering-gallery modes of microtoroidal resonators serve as quantum registers to store quantum information. By coding the qubits of NV centers into decoherence-free subspaces, quantum information encoded in logical qubits is protected from collective dephasing, and quantum controlled-NOT and Toffoli gates between logical qubits from the same or different quantum nodes can be implemented. Compared with the previous works, our schemes are simpler and reduce the consumption of resources. Furthermore, the modularized design of multi-qubit quantum gates can be extended to other quantum platforms, which may lead to more efficient construction of quantum networks for distributed quantum computation and quantum communication.