About g-tensor uniformity of holes in Ge/SiGe heterostructures

A limiting factor for the controlled operation of multiple hole spin qubits in Ge/SiGe heterostructures is the variation of qubit frequencies and a seemingly random orientation of the in-plane g-tensor anisotropy. In contrast to previous work, we report on a device where the g-tensors axes of six qubits align. The dots are arranged in a Y-junction geometry. As previously reported in literature [1], we find a strong anisotropy of the g-tensors, with the out-of-plane component around 11 while the in-plane components are around 0.1 to 1. A principal axis direction of ~45° in-plane is observed, which cannot be explained by the device symmetry (3 arms at ~120°) or by an out-of-plane tilt (of less than 3°, too small to explain the g = 11 impact on the in-plane anisotropy). This suggest the in-plane principal axes direction in this device is dominated by a mechanism shared by all the dots, but its exact nature is still under investigation.

Additionally, we measure the avoided crossing of the singlet and spin-polarized triplet states of adjacent quantum dots, which is critical for the initialization and readout of our qubits, and we correlate it to the measured g-tensors.



[1] Hendrickx et. al. ,Nat. Mat. 23, 920 (2024)