Back-action Driven Electron Spin Singlet-Triplet Excitation in a GaAs Quantum Dot

TL;DR

This paper investigates how back-action from a quantum point contact induces spin singlet-triplet excitations in a GaAs quantum dot, revealing effects on qubit operations through a phenomenological model.

Contribution

It demonstrates back-action driven spin S-T excitations in quantum dots and introduces a model to quantify the excitation rate impacting qubit performance.

Findings

Back-action induces spin S-T excitations only in even-electron quantum dots.

RTS statistics can probe energy excited states affected by back-action.

The model quantifies the influence of back-action on spin qubit operations.

Abstract

In a single quantum dot (QD), the electrons were driven out of thermal equilibrium by the back-action from a nearby quantum point contact (QPC). We found the driving to energy excited states can be probed with the random telegraph signal (RTS) statistics, when the excited states relax slowly compared with RTS tunneling rate. We studied the last few electrons, and found back-action driven spin singlet-triplet (S-T) excitation for and only for all the even number of electrons. We developed a phenomenological model to quantitatively characterize the spin S-T excitation rate, which enabled us to evaluate the influence of back-action on spin S-T based qubit operations.