Applications of a hole spin qubit with spin-orbit switch*

Hole spins in Ge/Si nanowires feature a spin-orbit interaction that is both strong and gate-tunable [1,2]. Recently, this has led to the demonstration of a spin-orbit switch, which enables toggling a spin qubit between a fast control mode and a more coherent idling mode. The spin-orbit switch features a large electrical tunability of the Landé g-factor, which is of interest for individual qubit addressability in scaled up quantum circuits.
Here, we perform spectroscopy of a hole spin qubit in a Ge/Si nanowire and characterize the qubit parameters. In particular, we extract a strong dependence of the g-factor on gate voltage, detuning, and pulse amplitude. We use this g-factor control to implement a fast single-qubit logical phase-gate, enabling nanosecond control of the hole spin qubit around all principal axes. Next, we use the g-factor control to drive Rabi oscillations using continuous-wave microwaves, which could allow to improve coherence. Our results demonstrate several applications of a gate-tunable spin-orbit interaction, enriching the qubit manipulation toolbox using refined electrical control.
[1] arXiv:2007.04308
[2] arXiv:2006.11175