Quantum Kinetic Rates within the Nonequilibrium Steady State

TL;DR

This paper introduces a comprehensive method for defining and calculating quantum kinetic rates in nonequilibrium steady states, explicitly incorporating quantum effects and coherences, with applications to model systems like V-level and spin-boson models.

Contribution

It provides a general framework for quantifying quantum rates in NESS, including the effects of coherences and environment interactions, applicable to various quantum networks.

Findings

Quantum effects and coherences significantly influence rate processes.

The methodology is demonstrated on V-level and spin-boson models.

Conditions are identified where NESS rates can be derived perturbatively.

Abstract

The nonequilibrium steady state (NESS) of a quantum network is central to a host of physical and biological scenarios. Examples include natural processes such as vision and photosynthesis, as well as technical devices such as photocells, both activated by incoherent light (e.g. sunlight) and leading to quantum transport. Here, a completely general approach to defining components of a quantum network in the NESS, and obtaining rates of processes between these components is provided. Quantum effects are explicitly included throughout, both in (a) defining network components via projection operators, and (b) in determining the role of coherences in rate processes. As examples, the methodology is applied to model cases, two versions of the V-level system, and to the spin-boson model, wherein the role of the environment and of internal system properties in determining the rates is examined. In addition, the role of Markovian vs. non-Markovian contributions is quantified, exposing conditions under which NESS rates can be obtained by perturbing the nonequilibrium steady state.