Exploiting epitaxial strained germanium for scaling low noise spin qubitsat the micron-scale

Advancing the semiconductor spin qubit platform to the required scale and connectivity,

along with devising noise mitigation strategies, is challenged by disorder in the complex and

heterogeneous material stack. Here, we probe the noise characteristics of Ge hole spin-qubits in complex

devices able to host up to 14 quantum dots in two dimensions by exploiting epitaxially strained Ge/SiGe semiconductor heterostructures

of high crystalline and electrical quality. We investigate the 1/f charge noise trend across five decades of frequency, different electrostatic confinements, locations

on the Ge/SiGe wafer, and show an average low charge noise of S^1/2₀ = 0.3(1) μeV/√Hz at 1 Hz. We also observe large fluctuations in the voltage noise level (80 ± 60 μV/√Hz) at 10 mHz when changing the charge occupation of the quantum dots, suggesting a coupling to the noise environment that is highly

sensitive to the specific electrostatic configuration. By using single-hole spin qubits as sensitive noise probes,

we not only expand our investigation of charge noise but also explore the contribution of magnetic noise to qubit coherence. We evaluate the contribution to magnetic noise from both the

⁷³Ge in the quantum well and the ²⁹Si nuclear spin bath in the barrier.