Fast high-fidelity single-qubit gates for flip-flop qubits in silicon

The flip-flop qubit, encoded in the states with antiparallel donor-bound electron and donor nuclear spins silicon, showcases long coherence times, good controllability, and, contrast to other donor-spin-based schemes, long-distance coupling. Electron spin control near interface, however, is likely shorten relaxation time by many orders of magnitude, reducing overall qubit quality factor. Here, we theoretically study multilevel system that formed interacting derive analytical effective two-level Hamiltonians without periodic driving. We then propose an optimal scheme produces fast robust single-qubit gates presence low-frequency noise relying on parametrically restrictive sweet spots. This increases considerably both