A triangular triple quantum dot with tunable tunnel couplings

TL;DR

This paper reports the fabrication and characterization of a tunable triangular triple quantum dot system with a novel gate geometry, enabling control over inter-dot tunnel couplings for quantum computing applications.

Contribution

It introduces a new gate design for creating a triangular triple quantum dot with tunable tunnel couplings and demonstrates control over charge occupancy and coupling strength.

Findings

Successful fabrication of a triangular triple quantum dot with tunable tunnel couplings.

Charge occupancy and tunnel couplings are controllable via gate voltages.

Measured tunnel couplings confirm the effectiveness of the gate design.

Abstract

A two-dimensional arrangement of quantum dots with finite inter-dot tunnel coupling provides a promising platform for studying complicated spin correlations as well as for constructing large-scale quantum computers. Here, we fabricate a tunnel-coupled triangular triple quantum dot with a novel gate geometry in which three dots are defined by positively biasing the surface gates. At the same time, the small area in the center of the triangle is depleted by negatively biasing the top gate placed above the surface gates. The size of the small center depleted area is estimated from the Aharonov-Bohm oscillation measured for the triangular channel but incorporating no gate-defined dots, with a value consistent with the design. With this approach, we can bring the neighboring gate-defined dots close enough to one another to maintain a finite inter-dot tunnel coupling. We finally confirm the presence of the inter-dot tunnel couplings in the triple quantum dot from the measurement of tunneling current through the dots in the stability diagram. We also show that the charge occupancy of each dot and that the inter-dot tunnel couplings are tunable with gate voltages.