Plants soak up some of the 10¹⁷ joules of solar energy that bathe Earth each second, harvesting as much as 95 percent of it from the light they absorb. The transformation of sunlight into carbohydrates takes place in one million billionths of a second, preventing much of that energy from dissipating as heat. But exactly how plants manage this nearly instantaneous trick has remained elusive. Now biophysicists at the University of California, Berkeley, have shown that plants use the basic principle of quantum computing—the exploration of a multiplicity of different answers at the same time—to achieve near-perfect efficiency.

Biophysicist Gregory Engel and his colleagues cooled a green sulfur bacterium—Chlorobium tepidum, one of the oldest photosynthesizers on the planet—to 77 kelvins [–321 degrees Fahrenheit] and then pulsed it with extremely short bursts of laser light. By manipulating these pulses, the researchers could track the flow of energy through the bacterium's photosynthetic system. "We always thought of it as hopping through the system, the same way that you or I might run through a maze of bushes," Engel explains. "But, instead of coming to an intersection and going left or right, it can actually go in both directions at once and explore many different paths most efficiently."

In other words, plants are employing the basic principles of quantum mechanics to transfer energy from chromophore (photosynthetic molecule) to chromophore until it reaches the so-called reaction center where photosynthesis, as it is classically defined, takes place. The particles of energy are behaving like waves. "We see very strong evidence for a wavelike motion of energy through these photosynthetic complexes," Engel says. The results appear in the current issue of Nature.

Employing this process allows the near-perfect efficiency of plants in harvesting energy from sunlight and is likely to be used by all of them, Engel says. It might also be copied usefully by researchers attempting to create artificial photosynthesis, such as that in photovoltaic cells for generating electricity. "This can be a much more efficient energy transfer than a classical hopping one," Engel says. "Exactly how to implement that is a very difficult question."

It also remains unclear exactly how a plant's structure permits this quantum effect to take place. "[The protein structure] of the plant has to be tuned to allow transfer among chromophores but not to allow transfers into [heat]," Engel says. "How that tuning works and how it is controlled, we don't know." Inside every spring leaf is a system capable of performing a speedy and efficient quantum computation, and therein lies the key to much of the energy on Earth.

4 Comments

1. 1. sjones 11:19 AM 10/3/08

   Truly mind-blowing. But,wait, if simple plants use quantum computation to determine optimal energy pathways, is it too much of a leap to think that neurons evolved to optimize information pathways using similar methods?
   
   Quantum computing could already be here - between your ears.

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2. 2. Bob12 06:53 PM 11/23/08

   that is like so cool!!!!

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3. 3. georgehants 05:01 AM 2/7/10

   Does this mean the average "scientist" might have to become familiar with quantum theory.
   Will after 100 years, quantum theory be recognized as an importent part of everyday life.
   Will students wishing to look a little further than the Carnot cycle not be discouraged by teachers where the word quantum brings out a cold sweat.
   Will funding reserved for reductionist, mechanical research only, because the people concerned who understand nothing of progress and only wish to maintain the status quo until they retire as experts in their particular field, now become available to clever open minded young researchers to at last move on with reality.
   Can one of the most important aspects of science now be taught to 8 year olds as it should have been 50 years ago.
   All it says is the world is a much more wonderful and mysterious place than the average "scientist" has tried to maintain.

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4. 4. Joe Physics 01:10 PM 7/4/10

   Now wait just a minute. A green photon has a minimum size of ~400nM (the wavelength), and the molecules involved are at most a few 10's of nanometers across, and we are surprised that light is behaving as a wave and can affect different part of the molecule simultaneously?
   This is not "Quantum Computing" as it involves no entanglement of multiple photons.
   This looks like another hyped up use of trendy buzzwords to make headlines, search engines all to excite the gullible. Shame on you SA. Be a little more critical before parroting the hype/

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