Fun with Liquid Nitrogen

The mere mention of the phrase “quantum mechanics” is enough to strike fear into the hearts of anyone who’s not a physicist. This is probably doubly true for anyone who is a physicist. Back in my early collegiate days when I was a Physics major I was required to take QM as a sophomore. It didn’t work out. 2 years later I graduated with a degree in Neurobiology instead. It made more sense to me.

A reporter once asked Richard Feynman, Scientist and Four-Dimensional Space-Pimp, to explain his ground-breaking work in the field of quantum electrodynamics (QED) that garnered him a Nobel Prize at a level that the average person could understand. Feynman replied:

• “If I could explain it to the average person, I wouldn’t have been worth the Nobel Prize.”

Which is more or less how most people – myself included – see QM: the ultimate in intractable knowledge that is so theoretical it doesn’t even seem real. Because, well, it’s really, really tiny, right? And really, really tiny things don’t seem real to us, unless you’re a crackpot who believes that the LHC will create a black hole that will swallow the Earth. Hint: it won’t (link thoroughly explains why).

Even a certain famous cat used to describe the theory of quantum entanglement is only a thought experiment and doesn’t seem to affect reality in our minds. Well, unless you’re a robot:

But is there a way we can understand an effect of quantum mechanics? One phenomenon known as quantum coherence states that if a sub-atomic entity such as a photon or an electron that exists in a state of wave-particle duality – that is, it behaves like a wave and like a particle at the same time (imagine a subwoofer covered in sand to get your head around how this might look) – when given two potential paths down which to travel will not “choose” one path but will go down both paths simultaneously.

Trippy, huh? It also means that the electrons or photons will mostly travel down the optimal (shortest and with least resistance) path but will also travel down less-optimal paths. This might be hard to visualize, but it’s actually been known to happen for far longer than QM has been well-described: it was first discovered by Thomas Young about 200 years ago in his famous double-slit experiment with light interference:

(Dr. Quantum tends to massively dramatize things but the basic idea’s still true. And I thought I’d go with a cartoon theme today.)

Which is all and good if you’re particularly interested in lasers or, I don’t know, maybe building a Tesla death ray (and I know you are, don’t lie). But does it have any daily real-world applications that could not be performed without it? Actually, yes, if you’re a plant. It turns out that quantum coherence is the means by which photosynthesis is such an extraordinarily efficient process. I mean, think about it. The Second Law of Thermodynamics states that making smaller molecules out of bigger ones is always going to be an easier process than making bigger molecules out of smaller ones. It’s how we get our energy from metabolic processes. But plants do the opposite by taking carbon dioxide and water – two small molecules – and turning them into water and sugars – a small molecule and a substantially bigger one. And all they use is the light from the sun to power it. Clearly they’ve got a trick up their sleeves. Or… phloem.

It’s been suggested for a while now that quantum coherence is going on inside the chloroplasts. There are these odd molecules dubbed antenna pigments that seemed to really help photosynthesis along, but it wasn’t clear exactly how they accomplished that. So, in a study published in Nature this month, a group of researchers based out of the University of Toronto decided to look at photosynthesis in algae by bouncing very short laser pulses off the algae’s antenna pigment molecules and discovered that the photons shunted by these molecules did not travel on one discrete path every time but instead traveled on several different possible paths at the same time before finally resolving a direction, thereby greatly increasing the efficiency with which light is captured into chemical energy over what classical physics would predict.

If you’re confused now, don’t worry. Like Feynman said, if it wasn’t confusing, it wouldn’t be such an interesting and profoundly enigmatic field of research. Still, this has shown that quantum mechanics can have an effect not just in a physics laboratory but in biological organisms. On a really important process, too. After all, we kind of like all that oxygen and chemical energy plants create.

Now that we know their secret, though, this might mean that in the future we can create technology based on this photosynthetic pathway to build highly efficient, cheap forms of generating solar energy that will make our present solar panel technology look antiquated by comparison. Heck, if we’re really lucky we might even be able to combine it with quantum tunneling and harvest our energy directly from space, getting around that tricky atmosphere and magnetic field the Earth uses to deflect most light coming from the sun. All this might be a long way away – especially the parts with teleporting energy – but since the sun provides far more energy than we could ever possibly use, it’s definitely a viable avenue of research throughout the 21st century.

Plants, man. Who knew?

('’)