Level spectrum and charge relaxation in a silicon double quantum dot probed by dual-gate reflectometry

TL;DR

This study employs dual-gate radio-frequency reflectometry to analyze charge states and energy spectra in a silicon double quantum dot, revealing charge relaxation dynamics through phase shift signatures.

Contribution

It introduces a dual-gate reflectometry method for comprehensive charge and energy level analysis in silicon double quantum dots, including charge relaxation insights.

Findings

Complete charge stability diagram obtained

Charge transitions detected via phase shifts

Charge relaxation rates inferred from reflectometry signatures

Abstract

We report on dual-gate reflectometry in a metal-oxide-semiconductor double-gate silicon transistor operating at low temperature as a double quantum dot device. The reflectometry setup consists of two radio-frequency resonators respectively connected to the two gate electrodes. By simultaneously measuring their dispersive response, we obtain the complete charge stability diagram of the device. Charge transitions between the two quantum dots and between each quantum dot and either the source or the drain contact are detected through phase shifts in the reflected radio-frequency signals. At finite bias, reflectometry allows probing charge transitions to excited quantum-dot states thereby enabling direct access to the energy level spectra of the quantum dots. Interestingly, we find that in the presence of charge transport across the two dots the reflectometry signatures of interdot transitions display a dip-peak structure containing quantitative information on the charge relaxation rates in the double quantum dot.