Characterising the hole g-factor in lightly strained Ge/SiGe quantum wells with applications for hole spin qubits

Holes in strained germanium have emerged as a potential system for building spin qubits, with recent demonstrations of a four qubit processor [1,2]. In this work we show that the strain can be used to alter the g-factor of the hole system in germanium. We first show that a lightly strained germanium quantum well can confine a two-dimensional (2D) hole gas with high mobility, low percolation density and low effective mass [3]. We measure the g-factor anisotropy of the 2D system and find a larger g-factor anisotropy than more strained germanium quantum wells. This result suggests that strain in germanium can be used to tune the magnitude of the spin-orbit coupling of holes. This may allow for faster spin-qubit driving or finding "sweet spots" in qubit operation [4].



References:

[1] N. Hendrickx et al Nature 577, 487 (2020)

[2] N. Hendrickx et al Nature 591, 580 (2021)

[3] M. Lodari et al Appl. Phys. Lett. 120, 122104 (2022)

[4] Z. Wang et al , npj Quantum Information 7, 1 (2021)