The Mystery of Quantum Coherence in Photosynthesis is Solved... Molecular Vibration, Not Electrons, is Key

• A study published in the international journal Science Advances comprehensively reexamines and clarifies the previous interpretations of quantum coherence signals observed in photosynthetic complexes. 
• It proves that the long-lived quantum coherence signals are not of pure electronic origin, but rather originate from protein molecular vibrations in the electronic ground state. 
• It presents the biophysical insight that, even without fragile macroscopic electronic coherence, nature utilizes protein molecular vibrations and energy dissipation to maximize the efficiency of energy transfer in photosynthesis. 

[Quantum Biology Society]

Photosynthesis is the most marvelous and highly optimized energy transfer process created by nature. Recently, the scientific community enthusiastically embraced the hypothesis that the remarkable energy efficiency of photosynthesis is due to pure quantum coherence, sparking a renaissance in the field of quantum biology. However, it has recently been revealed that the true identity of these signals is not the quantum dance of electrons, but the vibrations of protein molecules, once again turning the tide in the academic community.

The paper titled "Quantum biology revisited," published in the international journal Science Advances, is an achievement by a multinational joint research team—including the Massachusetts Institute of Technology (MIT), the Max Planck Institute, and Lund University—that reanalyzed two-dimensional (2D) electronic spectroscopy data to reveal the true origin of photosynthetic quantum effects.

■ The True Identity of Quantum Coherence is Molecular Vibration

In the past, researchers interpreted the long-lived oscillatory signals observed in photosynthetic proteins like the Fenna-Matthews-Olson (FMO) complex as evidence of electronic quantum coherence. However, this study clearly demonstrates that these signals are not interexciton coherence stemming from pure electronic interactions, and that such electronic coherences disappear very rapidly within 50 to 75 femtoseconds (fs) at physiological temperatures, meaning they cannot play a functional role in energy transfer. The observed long-lived signals actually originate from phenomena such as Raman-active ground-state vibrations, where the protein scaffold itself vibrates. In other words, what was observed was not the pure quantum mechanical entanglement of electrons, but the precise physical tremors of molecules.

■ Nature's Wisdom: Exploiting Dissipation Rather Than Avoiding It

In a warm and wet biological environment, the quantum coherence of electrons undergoes decoherence, breaking down within an extremely short time. Nature, rather than trying to forcefully maintain a quantum state to avoid this environmental dissipation, actively exploits it. The protein environment precisely tunes the energy of each pigment and couples it with molecular vibrations, helping the energy to flow rapidly and efficiently downhill toward the reaction center without waste.

■ A New Paradigm in Quantum Biology

While this research shatters the previous illusion that pure electronic coherence directly dictates energy transfer in photosynthesis, it paradoxically reveals even more deeply how sophisticated nature's design is. By re-establishing the link of how the microscopic quantized world emerges into the macroscopic, essentially classical biological world, it provides a higher level of understanding of life phenomena. This groundbreaking insight is expected to provide a more realistic and powerful physical foundation for the future design of high-efficiency artificial photosynthetic systems and next-generation solar cell materials. 

https://www.science.org/doi/10.1126/sciadv.aaz4888