Tuning inter-dot tunnel coupling of an etched graphene double quantum dot by adjacent metal gates

TL;DR

This paper demonstrates that the inter-dot tunnel coupling in etched graphene double quantum dots can be precisely tuned over a broad range using adjacent metal gates, enhancing graphene's potential for quantum computing applications.

Contribution

It introduces a method to continuously and monotonically control tunnel coupling in graphene DQDs with a single gate, overcoming previous disorder-related limitations.

Findings

Tunnel coupling can be tuned by a factor of four with a single gate.

Electron addition modulates tunnel coupling monotonically.

Control over tunnel coupling range is significantly improved.

Abstract

Graphene double quantum open the possibility to use charge or spin degrees of freedom for storing and manipulating quantum information in this new electronic material. However, impurities and edge disorders in etched graphene nano-structures hinder the ability to control the inter-dot tunnel coupling, tc,the most important property of the artificial molecule. Here we report measurements of tc in an all-metal-gates-tuned graphene DQD. We find that tc can be controlled continuously about a factor of four by employing a single gate. Furthermore, tc, can be changed monotonically about another factor of four as electrons are gate-pumped into the dot one by one. The results suggest that the strength of tunnel coupling in etched DQDs can be varied in a rather broad range and in a controllable manner, which improves the outlook to use graphene as a base material for qubit applications.