Dispersive cavity-mediated quantum gate between driven dot-donor nuclear spins

Nuclear spins show exceptionally long coherence times but the underlying good isolation from their environ-ment is a challenge when it comes to controlling nuclear spin qubits. A particular difficulty, not only for nuclear spin qubits, is the realization of two-qubit gates between distant qubits. Recently, strong coupling between an electron spin and microwave resonator photons as well as a microwave resonator mediated coupling between two electron spins both in the resonant and the dispersive regime have been reported and, thus, a microwave resonator mediated electron spin two-qubit gate seems to be in reach. Inspired by these findings, we theoretically investigate the interaction of a microwave resonator with a hybrid quantum dot-donor (QDD) system consisting of a gate-defined Si QD and a laterally displaced 31P phosphorous donor atom implanted in the Si host material. We find that driving the QDD system allows to compensate the frequency mismatch between the donor nuclear spin splitting in the MHz regime and typical superconducting resonator frequencies in the GHz regime, and also enables an effective nuclear spin-photon coupling. While we expect this coupling to be weak, we predict that coupling the nuclear spins of two distant QDD systems dispersively to the microwave resonator allows the root implementation of a resonator-mediated nuclear spin two-qubit iSWAP gate with a gate fidelity approaching 90%.

Automated summary

Nuclear spins have long coherence times, but isolating them from the environment for controlling nuclear spin qubits is challenging. Strong coupling between an electron spin and microwave resonator photons, as well as microwave resonator mediated coupling between two electron spins, has been reported. Inspired by these findings, we theoretically investigate the interaction of a microwave resonator with a hybrid quantum dot-donor (QDD) system. By driving the QDD system, we can compensate the frequency mismatch and enable effective nuclear spin-photon coupling. Coupling the nuclear spins of two distant QDD systems to the microwave resonator allows the implementation of a resonator-mediated nuclear spin two-qubit iSWAP gate with a gate fidelity approaching 90%.