Do photosynthetic complexes use quantum coherence to increase their efficiency? Probably not

TL;DR

This study evaluates whether quantum coherence significantly enhances the efficiency of photosynthetic complexes, finding that such coherence has minimal impact under natural conditions and suggesting other evolutionary factors influence their structure.

Contribution

The paper provides a direct assessment of quantum coherence effects on photosynthetic efficiency using an open quantum systems approach, revealing minimal influence of coherence.

Findings

Quantum coherence is present but does not significantly boost efficiency.

Efficiency is largely unaffected by structural parameters in the mixed quantum-classical regime.

Natural complexes operate in a regime dominated by dephasing-assisted transport.

Abstract

Answering the titular question has become a central motivation in the field of quantum biology, ever since the idea was raised following a series of experiments demonstrating wave-like behavior in photosynthetic complexes. Here, we report a direct evaluation of the effect of quantum coherence on the efficiency of three natural complexes. An open quantum systems approach allows us to simultaneously identify their level of "quantumness" and efficiency, under natural physiological conditions. We show that these systems reside in a mixed quantum-classical regime, characterized by dephasing-assisted transport. Yet, we find that the change in efficiency at this regime is minute at best, implying that the presence of quantum coherence does not play a significant role in enhancing efficiency. However, in this regime efficiency is independent of any structural parameters, suggesting that evolution may have driven natural complexes to their parameter regime in order to "design" their structure for other uses.