Coupled vertical double quantum dots at single-hole occupancy

TL;DR

This paper demonstrates control over vertical double quantum dots in a silicon-germanium heterostructure, enabling precise charge state manipulation and opening new avenues for quantum simulation and computing.

Contribution

It introduces a method to control and distinguish vertical double quantum dots in a heterostructure, utilizing capacitive differences and charge sensing.

Findings

Successful confinement of a single hole in each quantum well

Ability to tune to the (1,1,1,1) charge state

Potential for three-dimensional quantum dot systems

Abstract

Gate-defined quantum dots define an attractive platform for quantum computation and have been used to confine individual charges in a planar array. Here, we demonstrate control over vertical double quantum dots confined in a double quantum well, silicon-germanium heterostructure. We sense individual charge transitions with a single-hole transistor. The vertical separation between the quantum wells provides a sufficient difference in capacitive coupling to distinguish quantum dots located in the top and bottom quantum well. Tuning the vertical double quantum dot to the (1,1) charge state confines a single hole in each quantum well beneath a single plunger gate. By simultaneously accumulating holes under two neighbouring plunger gates, we are able to tune to the (1,1,1,1) charge state. These results motivate quantum dot systems that exploit the third dimension, opening new opportunities for quantum simulation and quantum computing.