Quantum botany?

Plants – the fairly ordinary green things that we see around us every day – have harnessed an incredible trick of quantum mechanics that we only learned very recently, according to American researchers. In fact, the quantum trick forms the basis of photosynthesis, the process that turns light energy into fuel that supports most of life on Earth.

A leaf

A leaf, stranger than you ever imagined. Image: Wikimedia

The researchers found that, using something called ‘quantum entanglement’, plants can use almost all of the energy they collect from sunlight to make food, in the form of sugar, from carbon dioxide and water by the process of photosynthesis. By comparison, the most advanced solar power cells we can build turn less than half of the sunlight they collect into useful energy.

Quantum entanglement – or ‘spooky action at a distance’, as Albert Einstein called it – is a bizarre quantum effect that allows two completely separate particles to act as one, even though they are not physically connected. This means that changing the state of one particle instantly changes the state of the other, and plants use this to move energy from where it is collected to where it can be used very quickly, so almost no energy is lost on the way.

Photosynthesis is probably the most important chemical process ever to evolve. It allows plants to take water, carbon dioxide and sunlight and create sugary food; food which sustains animal populations and, ultimately, us.

The surprising thing is that the fragile quantum effect on which it relies, and which was only discovered by man in 1935, works outside the laboratory. Scientists have created pairs of entangled particles in the lab, but the experiments were very delicate, working only under tightly-controlled conditions.

Quantum mechanics is really strange. The field of quantum physics was founded in the 1920s, and since then many weird quantum effects have been found. From Schrodinger’s cat (a cat in a box with a vial of poison can be both alive and dead) to Heisenbergs uncertainty principle (we can know where a particle is, or where it is going, but never both), its results seem to contradict how we intuitively expect the world to work, yet scientists are increasingly finding it underpins so much of what we take for granted.

Paper Reference: Sarovar, M., Ishizaki, A., Fleming, G., and Whaley, B. (2010). Quantum entanglement in photosynthetic light-harvesting complexes. Nature Physics. Published online 25 April 2010. doi:10.1038/nphys1652

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