# Suppression of charge noise using barrier control of a singlet-triplet qubit

## TL;DR

This study demonstrates that barrier control in singlet-triplet qubits significantly reduces charge noise compared to tilt control, especially at higher exchange interactions, enhancing qubit stability.

## Contribution

It provides a molecular-orbital-theoretic analysis showing how barrier control decreases charge noise and its dependence on impurity location and exchange interaction.

## Key findings

- Charge noise is smaller under barrier control than tilt control.
- Charge noise decreases as exchange interaction increases with barrier control.
- Impurity location affects the degree of noise reduction, with less improvement for impurities equidistant from dots.

## Abstract

It has been recently demonstrated that a singlet-triplet spin qubit in semiconductor double quantum dots can be controlled by changing the height of the potential barrier between the two dots ("barrier control"), which has led to a considerable reduction of charge noises as compared to the traditional tilt control method. In this paper we show, through a molecular-orbital-theoretic calculation of double quantum dots influenced by a charged impurity, that the relative charge noise for a system under the barrier control not only is smaller than that for the tilt control, but actually decreases as a function of an increasing exchange interaction. This is understood as a combined consequence of the greatly suppressed detuning noise when the two dots are symmetrically operated, as well as an enhancement of the inter-dot hopping energy of an electron when the barrier is lowered which in turn reduces the relative charge noise at large exchange interaction values. We have also studied the response of the qubit to charged impurities at different locations, and found that the improvement of barrier control is least for impurities equidistant from the two dots due to the small detuning noise they cause, but is otherwise significant along other directions.