[Paper Review] Fundamental mechanisms of noise supported energy transfer in biological systems

Filippo Caruso, Alex W. Chin+3 more|arXiv (Cornell University)|Jan 28, 2009

Spectroscopy and Quantum Chemical Studies25 references9 citations

TL;DR

This paper identifies how environmental noise—specifically dephasing—can enhance quantum energy transfer in biological networks by suppressing destructive interference and enabling line broadening, thereby creating new transport pathways. Using analytical techniques to identify invariant subspaces in fully connected networks, the study explains the high efficiency and robustness of excitation transfer in photosynthetic complexes like the FMO complex and chlorosomes.

ABSTRACT

Excitation transfer through interacting systems plays an important role in many areas of physics, chemistry, and biology. The uncontrollable interaction of the transmission network with a noisy environment is usually assumed to deteriorate its transport capacity, especially so when the system is fundamentally quantum mechanical. Here we identify key mechanisms through which noise such as dephasing, perhaps counter intuitively, may actually aid transport through a dissipative network by opening up additional pathways for excitation transfer. We show that these are processes that lead to the inhibition of destructive interference and exploitation of line broadening effects. We illustrate how these mechanisms operate on a fully connected network by developing a powerful analytical technique that identifies the invariant (excitation trapping) subspaces of a given Hamiltonian. Finally, we show how these principles can explain the remarkable efficiency and robustness of excitation energy transfer from the light-harvesting chlorosomes to the bacterial reaction center in photosynthetic complexes and present a numerical analysis of excitation transport across the Fenna-Matthew-Olson (FMO) complex together with a brief analysis of its entanglement properties. Our results show that, in general, it is the careful interplay of quantum mechanical features and the unavoidable environmental noise that will lead to an optimal system performance.

Motivation & Objective

• To understand how environmental noise, typically seen as detrimental, can enhance energy transfer in quantum biological systems.
• To identify the physical mechanisms by which noise such as dephasing improves transport efficiency in dissipative networks.
• To develop an analytical framework for identifying invariant subspaces in Hamiltonian networks to study excitation trapping.
• To explain the high efficiency and robustness of energy transfer in photosynthetic complexes like the FMO complex and chlorosomes.

Proposed method

• Developed a novel analytical technique to identify invariant (excitation trapping) subspaces of a given Hamiltonian in fully connected networks.
• Applied the method to model excitation transfer in a fully connected network to study the role of noise in modifying transport pathways.
• Used numerical simulations to analyze excitation transport across the Fenna-Matthew-Olson (FMO) complex under noisy conditions.
• Investigated entanglement properties in the FMO complex to assess quantum correlations during energy transfer.
• Explored the interplay between quantum coherence, dephasing, and network topology to reveal noise-assisted transport mechanisms.
• Demonstrated that noise-induced line broadening and interference suppression enable additional transfer pathways.

Experimental results

Research questions

• RQ1 How can environmental noise such as dephasing enhance energy transfer in quantum biological networks rather than degrade it?
• RQ2 What physical mechanisms allow noise to suppress destructive interference and improve transport efficiency in dissipative networks?
• RQ3 How do line broadening effects contribute to the opening of new excitation transfer pathways in noisy networks?
• RQ4 To what extent can the principles of noise-assisted transport explain the efficiency of energy transfer in the FMO complex and chlorosomes?
• RQ5 What role do invariant subspaces in the Hamiltonian play in determining excitation trapping and transport robustness?

Key findings

• Noise, particularly dephasing, can enhance energy transfer by inhibiting destructive quantum interference in dissipative networks.
• Line broadening induced by noise creates additional pathways for excitation transfer, increasing overall transport efficiency.
• The analytical technique successfully identifies invariant subspaces in the Hamiltonian, revealing conditions under which excitation trapping occurs.
• Numerical analysis of the Fenna-Matthew-Olson (FMO) complex confirms that noise-assisted transport mechanisms contribute to its high efficiency.
• The study demonstrates that the interplay between quantum coherence and environmental noise leads to optimal system performance in photosynthetic complexes.
• Entanglement properties in the FMO complex are preserved under noise, suggesting quantum effects remain relevant in biological energy transfer.