Theory on electron-phonon spin dehphasing in GaAs multi-electron double quantum dots

TL;DR

This paper analyzes how electron-phonon interactions affect spin dephasing in multi-electron GaAs double quantum dots, revealing that biasing can improve the system's coherence properties compared to traditional two-electron setups.

Contribution

It introduces a theoretical framework for understanding electron-phonon dephasing in multi-electron quantum dots and demonstrates that biasing enhances the system's coherence advantage.

Findings

Dephasing rate increases with electron number in unbiased case.

Biasing reduces dephasing effects in multi-electron systems.

The merit figure improves with electron number in biased conditions.

Abstract

Recent studies reveal that a double-quantum-dot system hosting more than two electrons may be superior in certain aspects as compared to the traditional case in which only two electrons are confined (a singlet-triplet qubit). We study the electron-phonon dephasing occurring in a GaAs multi-electron double-quantum-dot system, in a biased case in which the singlet state is hybridized, as well as in an unbiased case in which the hybridization is absent. We have found that while the electron-phonon dephasing rate increases with the number of electrons confined in the unbiased case, this does not hold in the biased case. We define a merit figure as a ratio between the exchange energy and the dephasing rate, and have shown that in experimentally relevant range of the exchange energy, the merit figure actually increases with the number of electrons in the biased case. Our results show that the multi-electron quantum-dot system has another advantage in mitigating the effect of electron-phonon dephasing, which is previously under-appreciated in the literature.