Preserving Coulomb blockade in transport spectroscopy of quantum dots, by dynamical tunnel-barrier compensation

TL;DR

This paper introduces a dynamic tunnel-barrier compensation protocol that maintains Coulomb blockade in quantum dot transport spectroscopy, enabling stable charge control over a wide voltage range for scalable quantum computing.

Contribution

The novel protocol compensates for capacitive effects on tunnel barriers, preserving Coulomb blockade across a broad voltage span, improving quantum dot tuning for quantum computing applications.

Findings

Coulomb diamonds and excited states are clearly resolved.

The protocol extends the charge-occupancy tuning range.

Enhanced stability of Coulomb blockade observed.

Abstract

Surface-gated quantum dots (QDs) in semiconductor heterostructures represent a highly attractive platform for quantum computation and simulation. However, in this implementation, the barriers through which the QD is tunnel-coupled to source and drain reservoirs (or neighboring QDs) are usually non-rigid, and capacitively influenced by the plunger gate voltage (VP). In transport spectroscopy measurements, this leads to complete suppression of current and lifting of Coulomb blockade, for large negative and positive values of VP, respectively. Consequently, the charge-occupancy of the QD can be tuned over a rather small range of VP. By dynamically tuning the tunnel barriers to compensate for the capacitive effect of VP, here we demonstrate a protocol which allows the Coulomb blockade to be preserved over a remarkably large span of charge-occupancies, as demonstrated by clean Coulomb diamonds and well-resolved excited state features. The protocol will be highly beneficial for automated tuning and identification of the gatevoltage-space for optimal operation of QDs, in large arrays required for a scalable spin quantum computing architecture.