Seth Lloyd on Quantum Life

Seth Lloyd recently spoke at the Perimeter Institute for Theoretical Physics on how organisms have evolved to make use of quantum effects at the Perimeter Institute for Theoretical Physics.

According to Seth Lloyd, the phenomenon of birds migrating, photosynthesis, and even smelling and sneezing might be explained by quantum physics in addition to chemistry.

Lloyd likes to call this "quantum mechanical hanky-panky." Life, it turns out, has quite a lot to do with quantum mechanics, the area of physics first developed to understand what Albert Einstein and his contemporaries thought was some pretty strange behavior on the part of elementary particles like electrons.

Since then, scientists have shown how quantum physics could, theoretically, lead to faster, more efficient and more secure computers — an area of study called quantum computing. The fun part, Lloyd says, is that plants may have had a billion-year head start on actually building quantum computers. Lloyd, a renowned MIT professor, got interested in the quantum underpinnings of life in an unusual way. Back in 2007, the New York Times reported on a team of physicists who suggested that a particular microorganism called green sulphur bacteria acted like a quantum computer, and it was doing so to make photosynthesis — the process plants use to convert light energy into chemical energy — more efficient.

Green Sulphur Bacteria

At first, Lloyd and his colleagues, all experts in quantum computing, didn't take it seriously. "We thought this was really funny, (but) I got designated to look into it," he says. Although some of the details in the article were not accurate, it turned out that green sulphur bacteria really were doing quantum computations.

That discovery eventually led Lloyd to organize a series of small workshops at the Santa Fe Institute earlier this year on the relatively new field of quantum biology, which aims to understand how living things use quantum processes to become more efficient, more sensitive and generally better than classical physics and chemistry seem to allow.

The fundamental processes of living things go on at the level of atoms and molecules — the level quantum mechanics was designed to understand, so the fact that they behave according to quantum mechanical laws should not be too unreasonable. Physicists and others however, had thought biological processes lay in the so-called "semi-classical" domain, where quantum physics matters, but many of its finer details can be ignored.

For processes like photosynthesis, however, semi-classical physics only gets you so far.

Biologists and physicists had this much right: When plants absorb energy from the sun's rays, that energy gets passed among molecules called chromophores until it reaches a place called a reaction center, where the light energy is converted into chemical energy. Less clear was how, given the many paths the energy might take through the chromophores, plants could photosynthesize efficiently enough to stay alive. What Lloyd and others have figured out is that plants make it happen using a phenomenon called quantum coherence, meaning the energy can take all those paths at once and use information from each path to find the reaction center very quickly.

When Lloyd and other physicists looked beyond photosynthesis, they found many other places where quantum biology seems to be taking place.

New research on our highly discriminating sense of smell, for example, suggests that a molecule's quantum mechanical vibrations determine its odor — molecules with different shapes but that vibrate the same way smell the same, and molecules with the same shapes but different vibrations smell different. Moreover, birds might be using quantum mechanics when they migrate north and south. Scientists know that birds can tell when they're flying in line with Earth's magnetic field, but how they can tell remains a mystery. Recent experiments suggest birds can detect changes to the spin of an electron — sort of like the spin of a tether ball — as its gets pushed around by a magnetic field.

Birds, might actually be using a deeply quantum property of the tiny particles within their molecules as a built-in compass. The results are exciting, though Lloyd says he isn't sure where the field is headed. "One possibility is there's loads of quantum hanky-panky going on in these living systems that's just waiting to be discovered."