Excitation transfer through open quantum networks: a few basic mechanisms

TL;DR

This paper investigates fundamental mechanisms of quantum excitation transfer in open networks, identifying effects like congestion, unitarity, and staircase phenomena, with implications for biological and artificial energy transfer systems.

Contribution

It introduces and analyzes basic transfer effects in simple and complex quantum networks, aiming to uncover universal principles relevant to biological and artificial systems.

Findings

Identified three key phenomena: congestion, asymptotic unitarity, staircase effects.

Simple models reveal these effects can be fully understood.

Numerical results suggest relevance to biological and artificial energy transfer.

Abstract

A variety of open quantum networks are currently under intense examination to model energy transport in photosynthetic systems. Here we study the coherent transfer of a quantum excitation over a network incoherently coupled with a structured and small environment that effectively models the photosynthetic reaction center. Our goal is to distill a few basic, possibly universal, mechanisms or "effects" that are featured in simple energy-transfer models. In particular, we identify three different phenomena: the congestion effect, the asymptotic unitarity and the staircase effects. We begin with few-site models, in which these effects can be fully understood, and then proceed to study more complex networks similar to those employed to model energy transfer in light-harvesting complexes. Our numerical studies on such networks seem to suggest that some of the effects observed in simple networks may be of relevance for biological systems, or artificial analogues of them as well.