Operation speed and coherence time are two core measures for the viability of a qubit. Strong spin-orbit interaction (SOI) and relatively weak hyperfine interaction make holes in germanium (Ge) intriguing candidates for spin qubits with rapid, all-electrical coherent control. Here we report ultrafast single-spin manipulation in a hole-based double quantum dot in a germanium hut wire (GHW). Mediated by the strong SOI, a Rabi frequency exceeding 540 MHz is observed at a magnetic field of 100 mT, setting a record for ultrafast spin qubit control in semiconductor systems. We demonstrate that the strong SOI of heavy holes (HHs) in our GHW, characterized by a very short spin-orbit length of 1.5 nm, enables the rapid gate operations we accomplish. Our results demonstrate the potential of ultrafast coherent control of hole spin qubits to meet the requirement of DiVincenzo’s criteria for a scalable quantum information processor.

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.