Modeling the dynamics of a gate-defined electron spin qubit using Langevin equations

Abstract

Accurately modeling and simulating the single-electron spin qubit model of Loss–DiVincenzo within a semiconductor quantum dot heterostructure remains a significant challenge due to the incomplete understanding of the underlying noise processes and mechanisms. This work employs the quantum version of the Langevin equation framework, rooted in the spin-bath model theory, to systematically reframe and analyze all recognized physical noise effects. By constructing the model as a stochastic differential equation, it integrates quantum noise dynamics holistically rather than isolating specific noise effects. The primary contributors to qubit relaxation and decoherence are identified as direct spin flips, anharmonic oscillations, and random local fields. The dynamics of a single-spin qubit are presented within a semiconductor quantum dot, deliberately excluding external multi-qubit exchange interactions, which are assumed to be controlled or mitigated. The goal is to provide a detailed simulation analysis that combines various studies and bridges theory and experiments, offering a closer approximation to realistic scenarios.