# Coherent and incoherent theories for photosynthetic energy transfer

## TL;DR

This paper reviews both incoherent and coherent theoretical approaches to understanding the high efficiency of energy transfer in photosynthesis, highlighting recent developments in quantum models and their potential applications.

## Contribution

It provides a comprehensive summary of various theoretical models for photosynthetic energy transfer, emphasizing the importance of quantum coherence in natural and artificial systems.

## Key findings

- Quantum coherent effects have been experimentally demonstrated in photosynthesis.
- Multiple theoretical frameworks exist for modeling energy transfer, including hierarchical equations and quantum master equations.
- Understanding these models can aid in designing efficient artificial light-harvesting devices.

## Abstract

There is a remarkable characteristic of photosynthesis in nature, that is, the energy transfer efficiency is close to 100%. Recently, due to the rapid progress made in the experimental techniques, quantum coherent effects have been experimentally demonstrated. Traditionally, the incoherent theories are capable of calculating the energy transfer efficiency, e.g., (generalized) F\"orster theory and modified Redfield theory. However, in order to describe the quantum coherent effects in photosynthesis, the coherent theories have been developed, such as hierarchical equation of motion, quantum path integral, coherent modified Redfield theory, small-polaron quantum master equation, and general Bloch-Redfield theory in addition to the Redfield theory. Here, we summarize the main points of the above approaches, which might be beneficial to the quantum simulation of quantum dynamics of exciton energy transfer in natural photosynthesis, and shed light on the design of artificial light-harvesting devices.