CAOUS researchers provide insight into the role of quantum effects in photosynthesis

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.