Fast spin-valley-based quantum gates in Si with micromagnets

Electron spin qubits in silicon quantum dots hold promise for scalable quantum information processing. Recently, micromagnets have been employed to achieve high-fidelity spin manipulation and strong spin-photon coupling, which paves the way for the future scale-up of spin qubits. However, experiments on spin relaxation in silicon with micromagnets show a magnetic field dependence clearly different from previous theoretical and experimental results without micromagnets. We reveal that a synthetic spin-orbit field from micromagnets leads to such signatures in spin relaxation, where the interference effect plays a critical role. Furthermore, we show an enhancement of the electric dipole spin resonance and spin-photon coupling in a synthetic spin-orbit field as a result of the interference effect and the strong mixing at the spin-valley hotspot. The results enable novel schemes for fast quantum gates with potential applications in semiconducting quantum computing.