Spatial propagation of excitonic coherence enables ratcheted energy transfer

TL;DR

This paper presents a theoretical model demonstrating how quantum coherence can facilitate a ratchet mechanism for energy transfer in photosynthetic systems, suggesting a biological role for coherent oscillations in directing energy.

Contribution

The study introduces a novel theoretical model showing that quantum coherence can enable a ratchet effect in energy transfer, inspired by the Fenna-Matthews-Olson complex.

Findings

Quantum coherence can be created and maintained under natural conditions.

A ratchet mechanism for energy transfer is enabled by quantum coherence.

Long-range energy transfer is better understood via inter-complex coupling states.

Abstract

Experimental evidence shows that a variety of photosynthetic systems can preserve quantum beats in the process of electronic energy transfer, even at room temperature. However, whether this quantum coherence arises in vivo and whether it has any biological function have remained unclear. Here we present a theoretical model that suggests that the creation and recreation of coherence under natural conditions is ubiquitous. Our model allows us to theoretically demonstrate a mechanism for a ratchet effect enabled by quantum coherence, in a design inspired by an energy transfer pathway in the Fenna-Matthews-Olson complex of the green sulfur bacteria. This suggests a possible biological role for coherent oscillations in spatially directing energy transfer. Our results emphasize the importance of analyzing long-range energy transfer in terms of transfer between inter-complex coupling (ICC) states rather than between site or exciton states.