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Bacteria Exploit Quantum Coherence to Harvest Light

Researchers have found that purple bacteria use quantum coherence to harvest light during photosynthesis.

Chlorophyll molecules, which collect energy from light, are arranged in symmetrical rings inside purple bacteria. This geometric organisation is exceptionally good for light harvesting.

“Previous work proposed that quantum coherence, which describes the wave-like properties of particles, plays a role in light harvesting for purple bacteria,” says Dr Ivan Kassal of the ARC Centre of Excellence for Engineered Quantum Systems. “We found that the geometry adopted by the purple bacteria allows for quantum coherence. This research is significant as it provides evidence of quantum effects in a biological setting.”

There has been debate in the field about whether coherent effects are possible in photosynthetic systems at all. “We know now that quantum effects cannot be neglected in studies on biological light harvesting. This is a fertile ground for developing new technologies for simulating quantum systems in noisy environments.”

Kassal hopes to apply these findings to investigations of other species, including plants. The study, which has been published in the Journal of Physical Chemistry Letters, also opens avenues for research into whether quantum coherence already occurs in organic solar cells, and whether we can deliberately engineer that coherence to make them more efficient.

“If we can learn how they harvest light then we may be able to use these lessons to improve how we do artificial light harvesting,” Kassal says.