Image: "Pediastra, a flat colony of green algae", Wim van Egmond
Scientists at Berkeley report a breakthrough in the riddle of how bacteria can convert sunlight to energy at efficiencies nearing 100%. And the answer is more elegant and amazing than you will believe. Imagine your favorite Sci-fi character trapped in a maze. The future of the planet depends upon finding the fastest way out. Utilizing their quantum super-powers, they run all possible combinations of the maze simultaneously in parallel universes, calculating the best path before committing to any. Hurrah, the planet is saved! The truth behind quantum physics is always more complex than the sci-fi version, but reality is not too far off. Scientists have struggled to explain how plants can convert sunlight with high efficiencies. In the conventional model, a plant has many chlorophyll molecules, with only a few that are receptive to each specific bundle of energy that hits the plant. If electrons are hopping around looking for the right place to dock, it is a bit like trying to find the right path out of the maze. Energy should be wasted in each attempt which fails at a dead-end.
Now scientists led by chemistry prof Graham Flemming and lead author Gregory Engel at Lawrence Berkeley National Laboratory and the University of California, Berkeley, have achieved a breakthrough advance in understanding the photosynthesis process. The team fired ultra-short laser pulses at the proteins bacteria use in photosynthesis. The proteins were frozen to more than 300°F below zero, which makes the quantum effects easier to observe and reduces the "noise" due to greater motion in warmer molecules. What they found is quantum waves of energy exploring different excitation possibilities in the protein at the same time. Like a tiny quantum computer, the protein answers the question: which is the right path to convert this energy at highest efficiency? The scientists, and peers in the field, expect that a similar phenomenon will be found in plants, explaining nature's efficiency in using sunlight.
Understanding the role of quantum physics in efficient use of the sun's energy may lead to break-throughs in solar power technology. We know plants use solar energy 3 to 5 times better than the current state-of-the-art in silicon technology. If we can learn how they do it, perhaps mankind can do it better too.