A single hole spin with enhanced coherence in natural silicon*

Spin quantum bits in semiconductor appear to be one of the most promising technologies for the development of the quantum processor. Although electrons are the focus of modern research, holes exhibit many interesting physical properties. In particular, spin-orbit interaction allows a fully electrical  control of the hole spin qubit state. As a drawback, any external electric perturbation is likely to induce decoherence. Here we demonstrate for a single hole qubit in silicon the existence of sweet spots at which the qubit is decoupled from charge noise while keeping an efficient electrical driving. We first realize spin single-shot readout of the first hole accumulated in a natural silicon quantum dot made from an semi-industrial 300mm CMOS foundry. Subsequently, we characterize the hole spin g-tensor and its susceptibility to electric fields by coherent manipulation depending on the external magnetic field orientation. It reveals optimal operation points at which the longitudinal spin-electric susceptibility is minimal. At these sweet-spots, we measure an Hahn-Echo decay time $T2^echo = 100us while maintaining Rabi frequencies in the MHz range . This work opens new perspectives for quantum processing based on spin-orbit qubits.