Optimal control of a charge qubit in a double quantum dot with a Coulomb impurity

TL;DR

This paper investigates how optimized laser pulses can rapidly and efficiently localize charge in a double quantum dot system, even in the presence of Coulomb impurities, using advanced quantum control techniques.

Contribution

It introduces a two-step optimization protocol to maintain high-fidelity charge localization despite Coulomb impurity effects.

Findings

Optimized pulses achieve fast charge localization.

Impurities reduce localization efficiency, but the protocol mitigates this.

The method is validated through a two-electron quantum dot model.

Abstract

We study the efficiency of modulated laser pulses to produce efficient and fast charge localization transitions in a two-electron double quantum dot. We use a configuration interaction method to calculate the electronic structure of a quantum dot model within the effective mass approximation. The interaction with the electric field of the laser is considered within the dipole approximation and optimal control theory is applied to design high-fidelity ultrafast pulses in pristine samples. We assessed the influence of the presence of Coulomb charged impurities on the efficiency and speed of the pulses. A protocol based on a two-step optimization is proposed for preserving both advantages of the original pulse. The processes affecting the charge localization is explained from the dipole transitions of the lowest lying two-electron states, as described by a discrete model with an effective electron-electron interaction.