Tunable noise insensitivity combined with fast driving of a single hole spin qubit in Silicon.

Hole-spin qubits hosted by quantum dots in group IV semiconductors have emerged as leading candidates for large-scale quantum computing. Such qubits indeed exhibit strong spin-orbit coupling, which allows for their fast and all-electrical driving. However, this sensitivity to electric field is often accompanied by a longitudinal coupling to nearby electric fields, creating pathways for spin decoherence through charge noise. Here, we experimentally demonstrate the existence of ``sweetlines'' of magnetic field orientation where the qubit sensitivity to electric noise vanishes. At the same time, we show that these sweetlines contain maxima of driving efficiency leading to fast Rabi oscillations with a quality factor of up to 1200, thus forming optimal operating points for the qubit with both maximised coherence and operating speed. We additionally demonstrate the ample electrical tunability of the sweetline positions, providing a path to electrically align multiple qubits by to a shared optimal operation point. These results again demonstrate that hole spin qubits in silicon (and germanium) are very potent qubits that can be electrostatically engineered to overcome intrinsic variability.