Efficient and robust hopping gates in Si/SiGe quantum dots with enhanced spin orbit coupling

Single spin qubits in Si/SiGe quantum dots typically rely on micromagnets, high-frequency AC driving, and large magnetic fields, which raises scalability, dephasing, and heating concerns. We propose hopping-based single-qubit gates in a double dot formed in a``Wiggle Well" Si/SiGe heterostructure, where oscillations of Ge concentration along the growth direction enhance spin orbit coupling (SOC). A unitary transformation shows that this enhancement produces a misalignment of the spin-quantization axes between the two dots by an angle $\theta$. Our gate uses slow, purely electrical shuttling pulses that alternate the electron between dots and apply rotations to these tilted axes which yields an effective X-rotation. We evaluate the gate fidelity under realistic conditions, including finite ramp time, quasi-static charge noise, alloy disorder, and valley splittings. Across many noise/disorder realizations, the gate exhibits high average fidelity. Finally, comparing this gate with a conventional device with micromagnet-induced artificial SOC, we find up to two orders of magnitude lower infidelity in the Wiggle Well device. These results point to scalable, electrically controlled, high-fidelity spin qubits in silicon without micromagnets, microwave driving, or large magnetic fields.