Lusting after 100% energy efficiency? Photosynthesis’ quantum secret may hold key

For power conversion engineers it should be humbling to look at the near-100% efficiency with which plants convert sunlight into chemical energy – after all, the conversion efficiency of commercially available solar cells is only about 16-18%.

However, no one knows how photosynthesis works, despite its potential for solving much of the world’s energy problems. So it’s good news that researchers at the University of California, Berkeley, working with the U.S. Department of Energy’s Berkeley Lab have started to break photosynthesis’ code.

Photosynthesis’ secret sauce seems to be the speed with which it occurs — the transfer is so fast - virtually instantaneous — that energy isn't wasted as heat. " Virtually instantaneous" sounds like a quantum relationship, and indeed, the researchers found the answer to the mechanism in quantum mechanics.

“We have obtained the first direct evidence that remarkably long-lived wavelike electronic quantum coherence plays an important part in energy transfer processes during photosynthesis,” said Graham Fleming, the principal investigator for the study. “This wavelike characteristic can explain the extreme efficiency of the energy transfer because it enables the system to simultaneously sample all the potential energy pathways and choose the most efficient one.”

This all sounds so familiar to followers of quantum computing. I’m getting the feeling that within 5 years quantum mechanics will be taught in engineering classes rather than – or in addition to – physics classes. It will be just another technology tool. (Albeit an incredibly cool one.)

Results of the study are presented in the April 12, 2007 issue of the journal Nature; You can also read the summary, "Quantum Secrets of Photosynthesis Revealed."

(Image courtesy of Greg Engel, Lawrence Berkeley National Laboratory, Physical Biociences Division)