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.
@article{arxiv.2006.12340,
title = {Ultrafast coherent control of a hole spin qubit in a germanium quantum dot},
author = {Ke Wang and Gang Xu and Fei Gao and He Liu and Rong-Long Ma and Xin Zhang and Zhanning Wang and Gang Cao and Ting Wang and Jian-Jun Zhang and Dimitrie Culcer and Xuedong Hu and Hong-Wen Jiang and Hai-Ou Li and Guang-Can Guo and Guo-Ping Guo},
journal= {arXiv preprint arXiv:2006.12340},
year = {2022}
}