Sign-switching of superexchange mediated by few electrons under non-uniform magnetic field

TL;DR

This paper investigates how the superexchange interaction between distant spins in a quantum-dot array can be controlled and enhanced by varying the number of electrons in the mediator dot, with implications for scalable quantum computing.

Contribution

It demonstrates that increasing the number of mediating electrons and forming a triplet state enhances superexchange, providing insights for scalable quantum-dot networks.

Findings

Superexchange strength increases with more mediating electrons.

Forming a four-electron triplet further enhances superexchange.

Guides the design of scalable quantum-dot arrays.

Abstract

Long range interaction between distant spins is an important building block for the realization of large quantum-dot network in which couplings between pairs of spins can be selectively addressed. Recent experiments on coherent logical states oscillation between remote spins facilitated by intermediate electron states has paved the first step for large scale quantum information processing. Reaching this ultimate goal requires extensive studies on the superexchange interaction on different quantum-dot spatial arrangements and electron configurations. Here, we consider a linear triple-quantum-dot with two anti-parallel spins in the outer dots forming the logical states while various number of electrons in the middle dot forming a mediator, which facilitates the superexchange interaction. We show that the superexchange is enhanced when the number of mediating electrons increases. In addition, we show that forming a four-electron triplet in the mediator dot further enhance the superexchange strength. Our work can be a guide to scale up the quantum-dot array with controllable and dense connectivity.