Quantum “Magic” in Plants – Photosynthesis

We all know that plants take their energy from the sun. You might have learned in school that the process through which they turn small “particles” of light energy called photons into food is called photosynthesis. It might be surprising to learn that this is all linked to quantum mechanics, the strange theory that says a cat can be both dead and alive at the same time.

As weird as it sounds, quantum mechanics has predicted a multitude of phenomena. Light energy, carried by photons, travels from the Sun millions of kilometres to reach the cell of a plant—more specifically, a molecule called chlorophyll—kicking its electrons into excited states. The light energy is stored in one of these molecules in small energy packets named excitons.

The exciton must travel to a reaction centre where the energy it carries can be turned into food the plant can later use. But what path should the exciton take? If we think about it in classical (day-to-day, not quantum mechanical) terms, this small packet of energy would bounce around other molecules, dead ends, etc., until it randomly reaches the reaction centre.

Picture taken from this website.

However, scientists, while studying light-harvesting complexes such as certain bacteria and algae, have found that this is not the case. According to this theory, instead of taking one path until randomly reaching the reaction centre, the exciton explores multiple paths (a superposition of paths) at the same time. This makes the process remarkably efficient.

What makes this even more interesting is that this phenomenon does not happen inside a lab where scientists create an environment perfect for quantum phenomena to arise by keeping particles at insanely low temperatures, but rather, it happens in a warm, wet, and noisy environment.

Quantum biology is a growing field where scientists explore the ways living organisms make use of quantum phenomena. There are quite a few examples of this, such as bird navigation and enzyme reactions. The way organisms make use of quantum mechanics is fascinating and makes me wonder even more about what nature “knows” and we do not.

So next time you look at a plant, think about the quantum “magic” happening when a photon hits one of its leaves. Stay Curious!!!

Read More:
Quantum coherence in photosynthesis – Nature

Probing quantum features of photosynthetic organisms – npj Quantum Information

Thank you for reading!