Charge sensing of few-electron ZnO double quantum dots probed by radio-frequency reflectometry

TL;DR

This paper demonstrates radio-frequency reflectometry and charge sensing in ZnO quantum dots, enabling detection of single-electron charges and advancing ZnO's potential for quantum computing applications.

Contribution

The study develops a high-speed charge sensing technique in ZnO quantum dots using rf reflectometry, a novel approach for this material system.

Findings

Successful detection of single-electron charges in ZnO quantum dots.

Observation of few-electron double quantum dot charge stability.

Discussion of spin-state degeneracy and implications for spin readout.

Abstract

Zinc oxide (ZnO) has garnered much attention as a promising material for quantum devices due to its unique characteristics. To utilize the potential of ZnO for quantum devices, the development of fundamental technological elements such as high-speed readout and charge sensing capabilities has become essential. In this study, we address these challenges by demonstrating radio-frequency (rf) reflectometry and charge sensing in ZnO quantum dots, thus advancing the potential for qubit applications. A device is fabricated on a high-quality ZnO heterostructure, featuring gate-defined target and sensor quantum dots. The sensor dot, integrated into an rf resonator circuit, enables the detection of single-electron charges in the target dots. Using this setup, the formation of few-electron double quantum dots is observed by obtaining their charge stability diagram. Also, a charge stability diagram with a gate pulse sequence is measured. We discuss the strong electron correlation in ZnO, which leads to nearly degenerate spin-singlet and -triplet two-electron states in the (0, 2) charge state, and the perspectives on spin-state readout.