A depletion mode hole spin-qubit in Ge*

Spin qubits are considered to be among the most promising candidates for building a quantum processor [1] with group IV semiconductors standing out for their long coherence times and CMOS integrability. Recently, holes in Ge have proven scale-up beyond two qubits with a 4 Loss-DiVincenzo qubit device realized [2]. Here we demonstrate a spin qubit in a Ge/SiGe heterostructure realized with a single layer of confinement gates. We observe fast electrically controlled X and Z-rotations exceeding 100 MHz with dephasing times of 1 μs which we extend beyond 10 μs with echo techniques. The extracted noise spectral density suggests that the dephasing time is limited by low frequency fluctuations which we attribute to nuclear spins. The reported results demonstrate that holes in Ge are a viable candidate for integration into a large scale quantum processor.

[1] Vandersypen, L. M. K. et al. Interfacing spin qubits in quantum dots and donors-hot, dense, and coherent. npj Quantum Information 3 (2017).
[2] Hendrickx, N. W. et al. A four-qubit germanium quantum processor. arXiv: 2009.04268 [cond-mat] (2020).