Eliminating the confined dark-exciton qubit precession using an externally applied magnetic field

TL;DR

This study demonstrates how an external magnetic field can be used to precisely control and eliminate the precession of dark-exciton qubits in quantum dots, enhancing their potential for quantum information applications.

Contribution

It provides experimental and theoretical insights into controlling dark-exciton spin states via magnetic fields, enabling nullification of fine-structure splitting in quantum dots.

Findings

Magnetic field tuning of dark-exciton fine-structure splitting.

Polarization of dark-exciton spin states along crystallographic directions.

Conditions identified for stopping dark-exciton qubit precession.

Abstract

We investigate experimentally and theoretically the behavior of the confined dark exciton in an InAs/GaAs semiconductor quantum dot, under the application of an external magnetic field in Voigt configuration. We show that by varying the magnitude and direction of the external field one can accurately control the dark-exciton fine-structure splitting. In addition, we show that the dark-exciton spin state is approximately polarized along the cubic crystallographic directions [100] or equivalents. By comparing our experimental results with a model for the exchange and Zeeman interactions, we find the conditions for nullifying the fine-structure splitting between the two eigenstates of the dark exciton, thereby stopping its qubit precession.