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Roger Penrose is looking more credible
February 10, 2010 1:11 PM   Subscribe

Quantum processes involved in photosynthesis? "[A]lgae and bacteria may have been performing quantum calculations at life-friendly temperatures for billions of years. The evidence comes from a study of how energy travels across the light-harvesting molecules involved in photosynthesis. The work has culminated this week in the extraordinary announcement that these molecules in a marine alga may exploit quantum processes at room temperature to transfer energy without loss. Physicists had previously ruled out quantum processes, arguing that they could not persist for long enough at such temperatures to achieve anything useful." (via mr)
posted by kliuless (43 comments total) 9 users marked this as a favorite

 
I was always dismayed by the sort of handwavy explanations of energy transfer in photosynthesis I received in college. Now I am dismayed by this new-fangled and complicated explanation!
posted by Mister_A at 1:17 PM on February 10, 2010


When they say "transfer energy without loss", do they mean literally without loss, or just with minimal loss?
posted by East Manitoba Regional Junior Kabaddi Champion '94 at 1:20 PM on February 10, 2010


trippy!
posted by Stonestock Relentless at 1:21 PM on February 10, 2010


Nature continues to freak my shit out. In a good way.
posted by Red Loop at 1:27 PM on February 10, 2010 [1 favorite]


Dude, it's newscientist.
posted by Justinian at 1:33 PM on February 10, 2010 [4 favorites]


Can we add a 'newscientist' flag category?
posted by benzenedream at 1:34 PM on February 10, 2010 [3 favorites]


Wow, how was I able tell this was a new scientist link without even hovering over it?

Ugh. They're like the Daily Mail of science journalism.

Seriously, no one has "ruled out" quantum "processes" at room temprature or anywhere else. In fact, all sub atomic activity, and thus activity of molecules and everything else is "Quantum"

The idea of things like quantum tunneling being used in biological processes is nothing new, but that's totally different then quantum "Computing" which means actually solving mathematical problems using quantum effects. How would quantum "computing" make energy transfer more efficient?

According to the article, what's happening is that energy ends up in a super position of going through several different paths, and ends up taking the simplest one. But the superposition only lasts for 400 femtoseconds.

In order to build a real quantum computer, the superpositions need to be long lived, obviously.
posted by delmoi at 1:37 PM on February 10, 2010 [7 favorites]


@EMRJKC94

I guess if the structure recovered the energy used to compute the best path for absorption it would be lossless. My quantum computing understanding is nascent; but the computation being reversable, hence the energy recovery, is one big tenet of it. This seems to fall into that catagory.
posted by The Power Nap at 1:40 PM on February 10, 2010 [1 favorite]


Seriously, no one has "ruled out" quantum "processes" at room temprature or anywhere else. In fact, all sub atomic activity, and thus activity of molecules and everything else is "Quantum"

I just came in to say the same thing. Using "quantum" to describe anything is accurate, but it's like using a shotgun to drill a hole in the wall for a picture hanger.
posted by Burhanistan at 1:42 PM on February 10, 2010


this electron efficient path "computation" sounds really cool. this brings my list of quantum phenomena that actually have real, useful, surprising macroscopic outcomes to two.

the first is quantum tunneling and p-n junctions (enabling diodes and transistors) and that one ended up being pretty useful.
posted by dongolier at 1:45 PM on February 10, 2010


Photosynthesis uses quantum interactions to harvest light
posted by kliuless at 1:49 PM on February 10, 2010


The idea of things like quantum tunneling being used in biological processes is nothing new...

I was going to say. My copy of Asimov's book on photosynthesis (which is certainly no newer than the mid 60s, if that) discussed this.
posted by DU at 2:03 PM on February 10, 2010


Quantum tunneling isn't unknown in chemistry at all. Tautomerization is the tunneling of a proton between two electrostatic potential wells. Alternatively, it's a kind of structural isomerization that interconverts between two isomers by flipping a hydrogen and a double bond. It happens in proteins all the time, up to and including your DNA (Quantum Chemistry is going on INSIDE YOU, RIGHT NOW!).

So, the fact that a quantum tunneling mechanism has been found in the energy transfer in photosynthesis is at least plausible, and down right nifty, if true.
posted by bonehead at 2:17 PM on February 10, 2010 [2 favorites]


I should note, most tautomers interconvert at room temperature too.
posted by bonehead at 2:17 PM on February 10, 2010 [1 favorite]


Roger Penrose does not look more credible. While a few odd physicists may find his ideas about neuroscience credible, no neuroscientists do. This is because the basic processes that underly the function of nervous systems are understood, at least by those who have bothered to study them. Of all of those processes, the only ones that may proceed at a timescale anywhere near as short as 400 femtoseconds would be protein folding or binding. e.g., quantum mechanics is necessary to understand protein interactions, and pretty much nothing else.
posted by Humanzee at 2:20 PM on February 10, 2010


Does somebody want to translate this from crappy popsci speak for me? It sounds like they're either trying to describe quantum tunneling or Marcus theory, but it's hard to tell. Either way, not exactly a huge revelation.
posted by Dr.Enormous at 2:36 PM on February 10, 2010


42. That is all.
posted by scalefree at 2:57 PM on February 10, 2010


its not exactly tunnelling. from the Nature abstract they use the impossibility for two fermions (in this case electrons) to occupy the same quantum state. They excite two electrons so that they could otherwise (absent the above rule) occupy the same quantum states as one another they are said to be "entangled states" or exhibiting "quantum coherence". then later when you actually sample/observe the state of one the other's state is fixed as well. without paying $32 its hard to actually see what the actual outcome from the algae light antenna is, but newScientist claims this superposition of quantum states finds the least energy losing path for the photon as it travels from the antenna protein to the chlorophyll. that's the quantum "computation".
posted by dongolier at 3:04 PM on February 10, 2010


Sounds extraordinary!

Calling it computation seems to be a real misnomer to me though. The effect might be harnessed by people to perform computation, but.. does a rock rolling down a hill compute how fast it should be going?
posted by Chuckles at 3:09 PM on February 10, 2010


Note that my criticism could be leveled against any notion of quantum computation, not just this new discovery.
posted by Chuckles at 3:12 PM on February 10, 2010


What are Penrose's ideas on neuroscience?
posted by destro at 4:16 PM on February 10, 2010


I don't understand the New Scientist article at all, but at least there is a citation to the "newsworthy" publication: Collini et al., "Coherently wired light-harvesting in photosynthetic marine algae at ambient temperature," doi: 10.1038/nature08811, 2010. That paper doesn't mention quantum computers or quantum calculations. There is also a "News and Views" summary; those are usually more digestible for readers outside the field.

It seems like the background information here is the existence of "antenna" proteins which do the work of absorbing light in some crypto-algae, and transfer that energy to the "reaction centers" where the sugar happens. The antenna proteins are a sort of a Goldilocks complex, large enough that different pigments can absorb light and be excited without immediately transferring that energy to their neighbors, but small enough (this is the new information) that different excitations can interfere quantum-mechanically. The magic that allows the coherence seems to be a covalent bond between the pigments and the rest of the antenna.

It seems like the effect of this is energy storage: if the reaction center needs the energy from, say, four visible photons, the energy from one photon can move between different pigment groups on one antenna for a while before it gets lost.

The connection to quantum computing is made in an unpublished preprint. The connection seems to be "this coherence time is long enough to plausibly do a quantum computation," rather than "crypto-algae photosynthesis is a quantum computation" as reported by New Scientist.
posted by fantabulous timewaster at 4:21 PM on February 10, 2010 [1 favorite]


You know, I think New Scientist is getting better. That's a pretty good article, and I linked one a few months ago that I thought was outstanding. It might be good to re-evaluate the "New Scientist = Automatic Suck" stance.
posted by Malor at 4:23 PM on February 10, 2010


Oh, and what they're saying here is that this quantum superposition and subsequent tunneling is a form of computation; in this case, the alga is using it to transfer energy, not figuring out math problems. The 'computation' is in finding the correct path to move the energy where the alga wants it.
posted by Malor at 4:27 PM on February 10, 2010


Malor: that's like saying water 'computes' the path of least resistance while flowing down a hill, or something.
posted by delmoi at 4:30 PM on February 10, 2010 [1 favorite]


@bonehead

Not to be nit picky but tautomerization involves a multi-step mechanism that involves removal and addition of a hydrogen atom, not tunneling. The process is pH dependent which it surely would not be if it were intramolecular.
posted by dibblda at 5:11 PM on February 10, 2010


"It's quantum" is the new "It's complicated."
posted by mccarty.tim at 5:31 PM on February 10, 2010


This gives the kooks way too much power. If John Q. Public is to hear that leaves use magical quantum computing processes to turn sunlight into usable food, how's he to know for sure that water doesn't have a memory?
posted by mccarty.tim at 5:33 PM on February 10, 2010


Delmoi

Maybe it's more like a stream of water bypassing the path of initially-least resistance in order to take the path of overall-least resistance.

(Or something. Would the people who understand this stuff better than me keep talking please?)
posted by theDTs at 5:40 PM on February 10, 2010


that's like saying water 'computes' the path of least resistance while flowing down a hill, or something.

Well, I'm obviously no quantum physicist, but I think what they're saying here is that it's not just flowing downhill, it's finding an ideal path, and that they think this has implications for actual computing, not just energy transfer. 'Finding an ideal path' is another way of saying 'solving a very simple problem'. The fact that it's a quantum effect at all at 21C is a big deal, and they believe it's related to what quantum computers need to do.

I'll have to defer to anyone who has more of a clue than I do, but from a layperson's perspective, it looks pretty interesting.
posted by Malor at 7:51 PM on February 10, 2010


it's not just flowing downhill, it's finding an ideal path, and that they think this has implications for actual computing, not just energy transfer.

The key is that it has implications for computing, rather than actually performing computation.

When you take a lens, and then put a small aperture on the Fourier transform plane, and project the image on a screen, are you doing computation?

Another example.. At some time (maybe still?) very fast spectrum analysers used an acousto-optic system. Basically... Well, read this, and don't forget to search for the term "Acoustooptic Spectrum Analyzer".

If I recall correctly, the reason they do this is that they can't compute everything fast enough. So, they use physical properties to recreate a bunch of the math they need to do, and then just measure the output. The physical properties could be said to be doing the calculating, but that isn't really right. The designer of the device has found a clever way of using the physical properties to help calculate something. But the physical properties simply exist, they don't actually calculate.

Like computing the digits of pie by measuring a very precisely drawn circle.. Is the circle calculating pie for you?!?! :P
posted by Chuckles at 8:32 PM on February 10, 2010


Err.. Read this (and search for acoustooptic spectrum analyzer).
posted by Chuckles at 8:34 PM on February 10, 2010


It does not matter how scientists categorize or discover the processes of life or the universe. These phenomena go on, regardless of our ability to describe or understand them.

What I love is when fatheads dismiss things. Famous dismissals, "Junk DNA", and then everything else they can't quantify, or categorize, within their narrow spectra of interest.

Fact: This whole thing goes on whether we get it or not.

We are wasteful, lazy, and greedy. Nature is not. Nature is the queen of latency, the queen of the easy fix, the queen of creativity, in terms of efficiency, and the minimalist moves it takes to foment, and persist in life processes.

Unfortunately the truth of our current system, is that if money can't be made on it, it is not important. This is our downfall, and the downfall of large parts of the web of life. What we are doing with our inability to grasp the simple and the large, and our outrageous ability to "numericise" and rationalize, is losing the Whole Earth Ballgame.

What they have discovered is that we are dumb, and nature is smart.
posted by Oyéah at 8:51 PM on February 10, 2010


Well, remember that quantum level stuff doesn't directly map to physical stuff, and we can't use our intuition there the way we can with large-scale objects. From my understanding, what quantum bits are doing is seeking paths. The idea is to tangle together a number of 'qubits', and then put constraints on them defining a problem, and they'll find a path to the correct energy state that solves the problem, given the constraints. And they'll do so almost instantly.

I think what they're saying is that this is a form of that. The photon seeking a path is similar to a qubit falling into a deterministic state. Quantum-level effects by definition are not deterministic, but photosynthesis is causing a deterministic result, AND it's doing it at 21C.

If my very, very limited grasp of the field is correct, both these things are very important.
posted by Malor at 8:56 PM on February 10, 2010


According to the article, what's happening is that energy ends up in a super position of going through several different paths, and ends up taking the simplest one.

Let's take plants out of this entirely. Imagine I'm shooting a photon at a detector through some air, and then some glass and then some water. The photon takes the path where it's time of flight is fastest. So somehow it knows what it's going to encounter before it gets there and is calculating the optimal route from the word go.

It's almost like you could figure this out by summing contributions from each alternative space-time trajectory of the particles and calculating a transition probability amplitude. Richard Feynman got the Nobel Prize in Physics for this (along with Sin-Itiro Tomonaga and Julian Schwinger) in 1965!

So yes, it's exactly like like a stream of water bypassing the path of initially-least resistance in order to take the path of overall-least resistance.
posted by Kid Charlemagne at 9:36 PM on February 10, 2010 [1 favorite]


We are wasteful, lazy, and greedy. Nature is not. Nature is the queen of latency, the queen of the easy fix, the queen of creativity, in terms of efficiency, and the minimalist moves it takes to foment, and persist in life processes.

You've seen a platypus, right?
posted by one_bean at 11:15 PM on February 10, 2010


Nature is not anthropogenic.
posted by five fresh fish at 11:46 PM on February 10, 2010


anyone else who is trying to figure out the link between some quantum coherent electrons in a pigment and actual quantum computing should look at this link. the real benefit of QC lies in massive parallel computation, not in outbenchmarking an intel quadcore. by Feynman's definition the above phenomena qualifies as a quantum computation.

they create conditions for the superposition of quantum states, then as the coherence collapses, a single state is revealed---which in this case has the properties of the lowest energy path "solution". and also, in nature its very parallel in that every incoming photon's energy traverses this optimal energy path.
posted by dongolier at 1:24 AM on February 11, 2010


New Scientist Writers Attribute Everything Mysterious To 'Quantum Flux'
posted by Optimus Chyme at 6:55 AM on February 11, 2010


they use physical properties

quantum level stuff doesn't directly map to physical stuff

this reminds me of evolutionary FPGAs... or, suspiciously, like maxwell's demon! (or iron-plated snails ;)

defer to anyone who has more of a clue

here's sean carroll :P
We can think about this in terms of Feynman’s way of talking about quantum mechanics: rather than a particle taking a unique path between two points, as in classical mechanics, a quantum particle takes every possible path, with simple paths getting a bit more weight than complicated ones. In the case of the protein, different paths for the energy might be more or less efficient at any particular moment, but this bit of quantum trickery allows the energy to find the best possible route at any one time. Imagine at rush hour, if your car could take every possible route from your home to the office, and the time it officially took would be whatever turned out to be the shortest path. How awesome would that be?

The reason you can’t do that is that your car is a giant macroscopic object that can’t really be in two places at once, even though the world is governed by quantum mechanics at a deep level. And the reason for that is decoherence — even if you tried to put your car into a superposition of “take the freeway” and “take the local roads,” it is constantly interacting with the outside world, which “collapses the wave function” and keeps your car looking extremely classical.

Proteins in plants aren’t as big as cars, but they’re still made of a very large number of atoms, and they’re constantly bumping into other molecules around them. That’s why it’s amazing that they can actually maintain quantum coherence long enough to pull off this energy-transport trick. Previous studies had hinted at the possibility, but only by cooling the proteins down and shielding them from external jiggling. This new work happens at room temperature in the context of marine algae, so it seems to indicate that it can happen in real environments.
oh and btw Are Plants Really Using Quantum Entanglement In Photosynthesis?, cf. Quantum entanglement in photosynthetic light harvesting complexes

cheers!
posted by kliuless at 7:42 AM on February 11, 2010


tautomerization involves a multi-step mechanism

That's true for some cases, you're correct. I should have been more clear. Many tautomers do appear exchange protons by tunneling, however. At least, if you model the structure as a double well and assume tunneling between the wells, it matches the observed spectra. Some examples here, here and here.
posted by bonehead at 8:38 AM on February 11, 2010


Thanks, kliuless. When they say the plant is doing quantum computation, in other words, they're correct. It's not a form of computation we're very familiar with, but "finding the most efficient path" is restating the idea of "solving a problem", and that's also what quantum computers do. There's lots of scoffing in this thread, but it appears to be misplaced.

Again: New Scientist really seems to be improving. I gather they were once terrible, but I'm not sure they rate an instant dismissive handwave anymore.
posted by Malor at 9:58 AM on February 11, 2010


There is another article at Physorg that I found quite informative. Plus, it has pictures, yay!
posted by nTeleKy at 2:10 PM on February 11, 2010


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