Ultrafast and Electrically Tunable Rabi Frequency in a Germanium Hut Wire Hole Spin Qubit.

Hole spin qubits based on germanium (Ge) have strong tunable spin-orbit interaction (SOI) and ultrafast qubit operation speed. Here we report that the Rabi frequency ( f Rabi ) of a hole spin qubit in a Ge hut wire (HW) double quantum dot (DQD) is electrically tuned through the detuning energy (ϵ) and middle gate voltage ( V M ). f Rabi gradually decreases with increasing ϵ; on the contrary, f Rabi is positively correlated with V M . We attribute our results to the change of electric field on SOI and the contribution of the excited state in quantum dots to f Rabi . We further demonstrate an ultrafast f Rabi exceeding 1.2 GHz, which indicates the strong SOI in our device. The discovery of an ultrafast and electrically tunable f Rabi in a hole spin qubit has potential applications in semiconductor quantum computing.