Dispersive sensing of charge states in a bilayer graphene quantum dot

TL;DR

This paper demonstrates a dispersive charge sensing technique for bilayer graphene quantum dots using radio frequency reflectometry, enabling single-electron detection without auxiliary quantum devices.

Contribution

It introduces a novel dispersive readout method for gate-defined graphene quantum dots that simplifies detection by eliminating the need for additional quantum sensors.

Findings

Successful detection of individual charge states in a bilayer graphene quantum dot.

Operates effectively over a wide gate-voltage range.

Capable of probing excited states down to the single-electron level.

Abstract

We demonstrate dispersive readout of individual charge states in a gate-defined few-electron quantum dot in bilayer graphene. We employ a radio frequency reflectometry circuit, where an LC resonator with a resonance frequency close to 280 MHz is directly coupled to an ohmic contact of the quantum dot device. The detection scheme based on changes in the quantum capacitance operates over a wide gate-voltage range and allows to probe excited states down to the single-electron regime. Crucially, the presented sensing technique avoids the use of an additional, capacitively coupled quantum device such as a quantum point contact or single electron transistor, making dispersive sensing particularly interesting for gate-defined graphene quantum dots.