Ultrafast Operations of a Hole Spin Qubit in Ge Quantum Dot

Ke Wang, Gang Xu, Fei Gao, He Liu, Rong-Long Ma, Xin Zhang, Ting Zhang, Gang Cao, Ting Wang, Jian-Jun Zhang, Xuedong Hu, Hong-Wen Jiang, Hai-Ou Li, Guang-Can Guo, Guo-Ping Guo

Published 2020-06-22Version 1

Strong spin-orbit coupling and relatively weak hyperfine interaction make quantum dots in germanium a promising candidate for rapid, all-electrically quantum control of spin qubit. Here, we report two different modes of quantum operation in a single spin-qubit based on holes in germanium hut wire. By selecting a proper branch of spin resonances mediated by spin-orbit interaction, a Rabi oscillation exceeding 540 MHz is observed at a small magnetic field of 100 mT. Furthermore, we perform two-axis control of the spin qubit by applying a phase-tunable microwave modulation. A dephasing time is measured by Ramsey spectroscopy, and further extended by dynamic decoupling. The qubit has a rather high quality-factor of 90, for nanowire-based spin qubits.Based on numerical calculation of the Rabi frequency of these two modes, we confirm that the ultrafast control speed is caused by the large spin-orbit coupling strength of holes in germanium.Our results demonstrate the potential to further control the spin qubit with a faster frequency to meet the requirement of Divincenzo's criteria for quantum gates, when the spin-orbit coupling is properly enhanced while maintaining good coherence in this system.