Undoped accumulation-mode Si/SiGe quantum dots

TL;DR

This paper presents a novel undoped Si/SiGe quantum dot device with independent gate control, demonstrating precise tuning of tunneling rates and inter-dot coupling, advancing scalable quantum computing hardware.

Contribution

It introduces a device design combining low-disorder materials with an overlapping gate architecture for independent quantum dot control.

Findings

Tunneling rate control over nine orders of magnitude

Direct measurement of inter-dot tunnel coupling

Exponential dependence of tunneling on gate voltage

Abstract

We report on a quantum dot device design that combines the low disorder properties of undoped SiGe heterostructure materials with an overlapping gate stack in which each electrostatic gate has a dominant and unique function -- control of individual quantum dot occupancies and of lateral tunneling into and between dots. Control of the tunneling rate between a dot and an electron bath is demonstrated over more than nine orders of magnitude and independently confirmed by direct measurement within the bandwidth of our amplifiers. The inter-dot tunnel coupling at the (0,2)<-->(1,1) charge configuration anti-crossing is directly measured to quantify the control of a single inter-dot tunnel barrier gate. A simple exponential dependence is sufficient to describe each of these tunneling processes as a function of the controlling gate voltage.