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CAOUS researchers provide insight into the role of quantum effects in photosynthesis
January, 2012
Photosynthesis, the process by which energy from the sun is collected and stored as chemical
energy, is responsible for all life on this planet. Until recently it was assumed that classical
physics was sufficient to be able to understand these inherently biological processes. In 2007,
however, experiments from the Fleming group at UC, Berkeley, showed that quantum coupling between
different states in light-harvesting complexes can remain coherent for relatively long times (>200 fs).
These results have sparked much speculation and subsequent research by theoretical physicists and
chemists regarding the potential role of quantum effects and the role played by the protein matrix
in maintaining coherence and facilitating efficient energy transfer. To date, however, there have
been no experiments to clearly confirm or refute any of the predictions.
Researchers at Swinburne's Centre for Atom Optical and Ultrafast Spectroscopy have developed a
technique to isolate such long-lived quantum coherences in the light-harvesting complex from marine
algae. This technique has allowed them to probe the interactions between the excited states and the
rest of the complex in more detail than previously possible. These studies, have provided the first
clear measure of the decoherence time in tis system and provided the first observation of strong
coupling between the electronic transitions of the chromophores and the phonon modes of the protein
matrix that holds everything in place. Our observation of this strong coupling provides clear
experimental evidence that classical treatment of these interactions is not sufficient and that
models including the microscopic details of the coupling are required. Understanding the detail
of these interactions represents a significant step towards understanding the role of quantum
effects in photosynthesis.
This study was highlighted in physorg.com in January 2012.
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