Are Plants Really Using Quantum Entanglement In Photosynthesis?

Illustration for article titled Are Plants Really Using Quantum Entanglement In Photosynthesis?

A recent article in Scientific American suggested that plants use quantum entanglement in photosynthesis. What can this mean? The answer is more (and less) than expected. Take a quick look at quantum entanglement and find out why.

Quick Quantum Entanglement Facts:

a) Quantum entanglement happens when the quantum status of two particles is intertwined, like two cats in a sack.


b) As with two cats in a sack, determining the state of one particle (say, by lightly nudging the sack with your toe until one side twitches and says ‘meow') allows you to know the state of the other particle (the non-twitching, non-meowing particle).

c) Also as with two cats in a sack, changing the status of one particle (for example, playfully spritzing one cat with water) will allow you to change the status of the other particle (be ready for epic yowling, is what I'm getting at).

Illustration for article titled Are Plants Really Using Quantum Entanglement In Photosynthesis?

I'm sure at this point you're saying, "But then what will quantum entanglement do for me that two cats in a sack won't? Besides allowing me to avoid deep, painful, and permanently scarring scratches." Well, this is where things get, theoretically at least, weird.


If you were to stretch the twocatsack out until the two cats weren't sharing close quarters anymore, points b and c would no longer be true, more's the pity. Quantum entanglement, though, can mean that the distance between the particles is irrelevant.

Irrelevant in more ways than one. Not only will changing the state of one particle automatically change the state of the other, it will change the state of the other simultaneously. As in, at the exact same time, no matter what the distance between them. As in, communication between the entangled particles travels faster than light speed. (And leaves maximum cat-speed, approximately 30 miles-per-hour, in the dust.)


But that's not all that gets weird when distance is irrelevant. Anyone who has ever had to run laps on those days the gym teacher didn't feel like handing out basketballs knows that moving fast burns up energy. The longer distance a person runs, the more energy they expend. If distance doesn't matter, however, it wouldn't matter how far there is to go between the particles. Whatever it is that communicates between them moves infinitely fast, infinitely far, using the same energy and efficiency it would if the particles were next to each other.

It is this efficiency that the article makes the most of. Quantum entanglement allows plants to not only make the most of the energy they receive, but deliver that energy from leaves with near 100% efficiency. This means that plants have not only harnessed quantum entanglement, but have achieved feats of engineering that allow them to use it.


Unfortunately, the papers that the article name-checks are not as effusive as the article itself. They say that entanglement is a by-product, and that "it is however not clear whether it has a significant role in the functioning of light harvesting complexes." I'm sure that that's a relief to anyone who bought a house plant for company and is distressed to think that suddenly they're not the most intelligent being in their bedroom, but it will come as a disappointment to biochemistry geeks.

There is one aspect of this discovery that has everyone excited, though. Quantum entanglement, in a lab, is a fragile thing that occurs in extreme temperatures under controlled conditions. That it can occur in plants, or bacteria, is a heartening prospect. At the very least, that means that organic devices aren't just potentially the future for froofy things like clones and growing donor organs. They can be useful for physics, as well. Who knows? One day we might have quantum computers. Of course, we'll have to remember to water them.



Quantum Entanglement, Photosynthesis, and Better Solar Cells (Scientific American)


Quantum Entanglement in Photosynthesis? (the Foresight Institute)

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Being a theoretical particle physicist and someone who does not particularly like cats (there's got to be a correlation there somewhere), I feel compelled to provide a more accurate analogy/explanation for quantum entanglement, though nowhere nearly as entertaining as the cat analogy.

Not too long ago, a friend of mine who lives in the US asked me to explain QE in a way that was accurate but not too technical, so I'll just copy my message to him and paste it here.


Imagine that you and I each have a coin and that these two coins were "born" together, made from the same process, before I came to Denmark. Now, imagine that I bring my coin with me and that we decide to throw our respective coins and compare results. We devise some means of synchronizing our throws so that they occur simultaneously, that is, each throw of your coin happens at the same time I throw mine.

Now, suppose that our results are:

(T stands for tails, H for heads)



When I look at my results, without knowing about yours, I see that my results are what is expected from a fair coin. In fact, I could apply all kinds of randomness tests and I'd conclude that my coin is behaving like a random fair coin should.

When you look at your results, without knowing about mine, you reach the same conclusion about your own coin.

Yet, when we compare our results, we see that they are strongly correlated: every time I get a T, you get an H, and vice-versa. How can that be? The processes are supposed to be *independently* random, but they're not; somehow, their randomness are strongly correlated.

This is what's known as "quantum entanglement." Of course, it doesn't happen with coins, but if you take two electrons created by the same process (some particle reaction), for instance, and move them far away from one another, this is what happens: when you measure one electron's spin, it's either spin up or spin down, and it's a random process. Same with the other electron. However, their spin measurements are correlated just as with the coins.

Fine, you say, there must be some interaction, some kind of force that the electrons are exerting on one another (like electromagnetism or gravity, but not either one, because we understand both and know that they aren't it), so that when you measure one's spin, the other "knows" to flip its own spin the opposite way.

Ok, the problem is, though, that these measurements happened simultaneously, which means that whatever that interaction or force is, it's traveling faster than light, which contradicts the theory of relativity (which is one of the backbones of physics). This is known as the "EPR paradox" (EPR stands for Einstein, Podolsky, and Rosen, the three physicists who came up with it).

Quantum entanglement and the EPR paradox are still not well understood, but quantum entanglement is a real phenomenon, observed experimentally already. Whether the EPR paradox is a true paradox remains a mystery. If it is a true paradox, relativity will need to be fixed.