Non-Markovian Quantum State Diffusion for Spin Environments

TL;DR

This paper develops an exact non-Markovian quantum state diffusion method tailored for spin environments, enabling accurate modeling of strongly coupled quantum systems with spin baths at various temperatures.

Contribution

It extends NMQSD theory to spin baths, providing a new framework for simulating open quantum systems with non-Gaussian environments.

Findings

The method accurately describes dynamics of spin-bath systems.

Hierarchical expansion improves numerical computation in strong coupling regimes.

Applicable at both zero and finite temperatures.

Abstract

We introduce an exact open system method to describe the dynamics of quantum systems that are strongly coupled to specific types of environments comprising of spins, such as central spin systems. Our theory is similar to the established non-Markovian quantum state diffusion (NMQSD) theory, but for a spin bath instead of a Gaussian bath. The method allows us to represent the time-evolved reduced state of the system as an ensemble average of stochastically evolving pure states. We present a comprehensive theory for arbitrary linear spin environments at both zero and finite temperatures. Furthermore, we introduce a hierarchical expansion method that enables the numerical computation of the time evolution of the stochastic pure states, facilitating a numerical solution of the open system problem in relevant strong coupling regimes.