Single-electron double quantum dots in bilayer graphene

TL;DR

This paper reports on transport measurements of a bilayer graphene double quantum dot, demonstrating high tunability, control over charge states, and insights into spin and valley physics relevant for quantum computing applications.

Contribution

It introduces a highly tunable bilayer graphene double quantum dot device capable of controlling charge states and exploring spin-valley physics at the single-electron level.

Findings

Interdot tunnel rates around 2 GHz.

Capacitive and tunnel couplings increase with dot occupation.

Excited state spectra consistent with spin and valley conservation.

Abstract

We present transport measurements through an electrostatically defined bilayer graphene double quantum dot in the single electron regime. With the help of a back gate, two split gates and two finger gates we are able to control the number of charge carriers on two gate-defined quantum dot independently between zero and five. The high tunability of the device meets requirements to make such a device a suitable building block for spin-qubits. In the single electron regime, we determine interdot tunnel rates on the order of 2~GHz. Both, the interdot tunnel coupling, as well as the capacitive interdot coupling increase with dot occupation, leading to the transition to a single quantum dot. Finite bias magneto-spectroscopy measurements allow to resolve the excited state spectra of the first electrons in the double quantum dot; being in agreement with spin and valley conserving interdot tunneling processes.