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Quantum Coherence Found Fueling Photosynthesis 135

Gaygirlie writes "Ars Technica has posted an interesting article about new findings regarding quantum physics and photosynthesis. Their excerpt for the article: 'Physicists have found the strongest evidence yet of quantum effects fueling photosynthesis. Multiple experiments in recent years have suggested as much, but it has been hard to be sure. Quantum effects were clearly present in the light-harvesting antenna proteins of plant cells, but their precise role in processing incoming photons remained unclear.' Here's a little background info for those unaware of what coherence and quantum coherence are."
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Quantum Coherence Found Fueling Photosynthesis

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  • by Anonymous Coward on Wednesday December 07, 2011 @04:53PM (#38295110)

    "If you think you understand quantum physics, then clearly you don't."

    -Paraphrased Richard Feynman quote

  • Photoelectric Effect (Score:5, Interesting)

    by cosm ( 1072588 ) <thecosm3@@@gmail...com> on Wednesday December 07, 2011 @04:59PM (#38295184)
    I've seen some comments stating that 'meh photoelectric effect nothing new to see here'. While it is true that emission/absorption is subject to quantum mechanics, specifically the photo-electric effect being governed by the work function hf = phi - eV, with hf = hc/lambda, phi being the work-function of the material, and eV being the 'escape velocity' of the electrons; the point being that energy emitted/absorbed must satisfy the above relationship, otherwise the photo-electric effect does not work.

    What I believe this study is saying is that 'antennae' structures can act as a single quantum mechanical unit (the coherence) so that the incoming insolar radiation has more paths for electron conduction, since the transfer of energy/conduction of electrons is limited to the quantization by the work function, i.e., charge quantization limits the specific wavelengths/frequencies/energies of incoming photons that the plant can use to harvest energy, so in effect the evolution of these 'antennae' structures over time allows for a coherent systems that can act as single particles, with the different permutations of antennas allowing for vastly more permutations of allowed incoming wavelengths to satisfy the Schrodinger eqn (probably not dirac since these are most likely not relativistic interactions, at least the effects are negligible).

    I deal more with relativity and QED/QCD, but that's my interpretation of the article.
  • by Warwick Allison ( 209388 ) on Wednesday December 07, 2011 @05:21PM (#38295442) Homepage

    Any evolved system will use all possible inputs to its fitness function, simply because there isn't any mechanism of focusing. Unlike human design, which is all about making known mechanisms work and all but those mechanism are ignored, and even actively avoided. When early researchers used solid-state electronics to make genetic algorithms, often the "solution" only worked on the specific hardware circuit it was learnt on (not supposedly identical copies), because it relied on otherwise-undefined race conditions in the silicon.

    So don't be surprised if quantum effects are also used by your brain cells ... and by your anal sphincter.

  • "Decoherence" (Score:5, Interesting)

    by Theovon ( 109752 ) on Wednesday December 07, 2011 @05:47PM (#38295836)

    The way people often describe quantum decoherence is that an "observation" occurs that "collapses the wave function" and causes a superposition to converge to a single classical state. But I really think that's a misleading explanation. For one thing, surely the same phenomena occurred long before there were any intelligent observers, and secondly, scientists have observed things in states of quantum superposition WITHOUT causing decoherence.

    The way think of it (as a total amateur in the area) is that rather than the wave function representing probabilities of states, it represents the degrees to which something is in all of those states. An "observation" is just like many other interactions with the environment that change those probabilities (or degrees of state).

    Then there's the question of why subatomic particles (and some larger things) can be in states of quantum superposition, while larger things cannot. Penrose had a suggestion here. It's gravity. The more massive you are, the less your superimposed states can diverge from one another. Even a planet is in a state of superposition, but all of those states overlap so much relative to the dimensions of the object that you cannot distinguish them.

  • Re:But wait (Score:4, Interesting)

    by lennier ( 44736 ) on Wednesday December 07, 2011 @06:48PM (#38296542) Homepage

    Addendum Two.

    I believe the real reason the myth of the space colony still hangs around is that secretly (or not so secretly), otherwise intelligent people believe that the real problem with Earth isn't that we face resource shortages or biosphere degradation, but that those social and environmental problems are all really the fault of the ignorant swarming masses. And if we could only somehow get rid of the lower 99% of the Earth's population, we'd be fine.

    The attraction of the space colony is that it's believed to be an elite, gated community which by virtue of its extreme expense and difficulty, would attract only a "high class of colonist" along the lines of the first generation of US astronauts: university PhD educated, military trained, logical scientific thinkers, in the peak of physical fitness. Given such a genetic pool of "the right stuff", the space myth goes, these super-demigods couldn't help but create a new Utopia of scientific wonders, even given the huge resource disadvantage they started from.

    It's really an updated Atlas Shrugged idea: a Galt's Gulch in space populated only by Earth's Finest, who would sadly watch the dull, evil swarming masses back on Earth collapse into inevitable resource war and chaos, while the smart people up on the colony would of course just get on with making life better for everyone. As a political philosophy, it's basically Space Libertarianism, shading towards good old 1800s aristicratic racism: just putting "a better class of people" into a locked room, and keeping everyone else out, would create instant utopia. It's slightly less genocidal than out-and-out Fascism, since it just leaves Earth's masses to rot rather than actively killing them, but it harbours the same intense distrust and hatred of the untermensch as the worst excesses of WW2.

    The problem is, utopias simply don't work like that. There've been many attempts at creating closed, self-selected communities, and they always go bad. Not even thinking about cults, have you ever seen a university, political activist movement, or high-tech company in action? Have you seen the kind of petty squabbles that occur in our elite institutions? Do you really think things will be different in space?

    No. They won't be. And that's why the virtuous, pioneering Space Colony that can magic a healed biosphere and super-energy sources by sheer force of logic out of a desert of vacuum and hard radiation - just so long as they're not pestered by those ignorant savages down on Earth - is just that, a myth, and a fairly nasty one. We really need to put it behind us before it screws up our thinking even more than it has.

  • by slew ( 2918 ) on Wednesday December 07, 2011 @06:51PM (#38296592)

    Back in '07, this article was published...

    http://www.physics.gla.ac.uk/~dtngo/Article/Nature_446_782_2007.pdf [gla.ac.uk]

    As I understand this, in the classical photosynthesis model, energy transfer is sort of modeled like the incoming sunlight excites a population of light absorbing "antennea" pigments which transfer the energy to reaction centers where long term energy storage is initiated (e.g., the CO2->sugar conversion). If the energy transfer was "classically" photoelectric, you'd see a system where light excites a population of antenna of different pigments, which then re-emit the energy at a wavelength compatible with the photosynthesis.

    If this was true, you could potentially measure electric field and look for frequency of absorbtion and re-emission (they would look like 2 frequency peaks). However, if there were some sort of state coupling, you'd also see beat frequencies corresponding to the difference in energies between various pigments and the re-emission. That in itself is not that interesting, but the fact that when they sent in pulses, these frequencies corresponding to beat frequencies seems to persist longer than the expected coherence time which apparently suggests that coherence lasts long enough to transit all the way from the antenna/pigments to the location of energy conversion (in this case 660 femtoseconds).

    The next step is to hypothesize that you can use QM and treat the full system as essentially coherently absorbing light at with the exactly correct antenna/pigment and re-emitting it essentially lossless to the conversion point, rather than it absorbing a collection/population of antenna over a period of time (some of them efficiently, some of them less efficienty), and re-emitting the energy (the classical model). Of course this is a pretty big step and is not a constructive argument, but it is in line with observations about photosynthetic efficiency and there is now more measurements to back up the potential (QM/coherence) pathway which might be able to explain that efficiency..

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