Spin relaxation benchmarks and individual qubit addressability for holes in quantum dots

TL;DR

This study benchmarks hole spin relaxation times and demonstrates individual qubit addressability in germanium quantum dots, highlighting their potential for scalable, high-fidelity quantum computing.

Contribution

It provides the first benchmarks for spin relaxation times in hole quantum dots and explores qubit tunability and sensitivity, advancing quantum dot qubit technology.

Findings

Spin relaxation times up to 32 ms for single-hole quantum dots.

Large range of resonance frequency tuning for both single and multi-hole qubits.

Weak dependence of resonance frequency on neighboring gates, enabling individual addressability.

Abstract

We investigate hole spin relaxation in the single- and multi-hole regime in a 2x2 germanium quantum dot array. We use radiofrequency (rf) charge sensing and observe Pauli Spin-Blockade (PSB) for every second interdot transition up to the (1,5)-(0,6) anticrossing, consistent with a standard Fock-Darwin spectrum. We find spin relaxation times $T_1$ as high as 32 ms for a quantum dot with single-hole occupation and 1.2 ms for a quantum dot occupied by five-holes, setting benchmarks for spin relaxation times for hole quantum dots. Furthermore, we investigate the qubit addressability and sensitivity to electric fields by measuring the resonance frequency dependence of each qubit on gate voltages. We are able to tune the resonance frequency over a large range for both the single and multi-hole qubit. Simultaneously, we find that the resonance frequencies are only weakly dependent on neighbouring gates, and in particular the five-hole qubit resonance frequency is more than twenty times as sensitive to its corresponding plunger gate. The excellent individual qubit tunability and long spin relaxation times make holes in germanium promising for addressable and high-fidelity spin qubits in dense two-dimensional quantum dot arrays for large-scale quantum information.