6 ms·

Quantum Light Harvesting Hints at Entirely New Form of Computing

89 points by digisth 13y ago

TrainedMonkey 13y ago
This is actually interesting. If their theory is correct plants have essentially loss less and super fast way for photons to traverse a random network^1. 1: They claim it is random network, I am not sure if we can call specific protein truly random. There is also question of size, scale of this effect might be small enough that there will be no applicable technology that could utilize it yet.
- VladRussian2 13y ago
  in the original article they clear that it isn't a photon, it is exciton that does the traveling: http://arxiv.org/pdf/1311.4688v1.pdf http://arxiv.org/pdf/1311.4688v1.pdf "In these systems excitons initiated by the incoming photons should travel really fast throughout a chain of chromophores in order to reach the reaction center where they are converted to chemical energy." >loss less and super fast way for photons to traverse a random network^1. My understanding is it isn't exactly loss less. It is a trade-off. The "natural" QM way of simultaneous multi-path travel is the super fast way of finding the reaction center. The issue is that many of these multi-paths may interfere and as result some degree of "entrapment" happens significantly delaying the arrival at the reaction center (Anderson localization - on a lattice draw all possible ways from A to B, including loops, etc... and whenever paths pass through the same edge with different direction double the edge time on each path and given lattice complex enough the propagation would almost stall - very-very rough illustration). To minimize the delay, the nature seems to came up with workaround - [slightly] breaking the phases on different paths and it seems that coherence is still preserved so we still have multi-path simultaneity while the above mentioned Anderson localization is decreased because of phase mismatch. This phase breaking is result of interaction which causes some energy loss/dissipation.
deleted 13y ago
[deleted]
jheriko 13y ago
the writing smacks of pseudoscience sadly... the idea of 'a mix of quantum and classical' implies a lack of understanding of what quantum mechanics is and specifically the correspondence principle. when did these two things become separate in anything other than some categorisation of our theoretical understanding of things? The entire article is coloured with it which makes it hard to glean any valuable information from. The analogy (?) about light bouncing around proteins, superpositions and collapses is especially confusing. If you look at the paper it does seem genuine and without the hype and bad analogies. (although there is some quite bad grammar, and i am far enough from subjects i am comfortable with that this could be psuedoscience). What I get from this is 'we have done work on a very specific example of quantum computing in nature - that work provides evidence that such approaches are viable'
Xcelerate 13y ago
This is a really cool article! I've never heard of plants doing something like this. However, the article is written kind of sloppily. > Quantum states are highly fragile — sneeze and they disappear in a puff of smoke. No, quantum states never disappear. They just evolve in time. However, it is hard to isolate a system that you are assigning a state vector from its surroundings. > They say the processes behind light harvesting are a special blend of the quantum and the classical. This kind of misleadingly suggests that reality has separate quantum and classical components. That's not the case; everything is quantum. It's just that some things that occur cannot be described accurately with classical physics. > Because energy can exist in a superposition of states, it can travel a variety of routes around the network at the same time. And when it finds the correct destination, the superposition collapses, leaving the energy at the reaction centre. Light travels. Energy is just a number that's conserved in non-relativistic QM. Also, while I suppose you could describe light as traveling through every path at once (and I know a lot of physicists like to describe it this way too), it sounds much more mysterious than it needs to be to me. I would just say: "as the wavefunction evolves in time, its probability amplitude spreads throughout space". > Another is the quantum zeno effect, the paradoxical phenomenon in which an unstable state never changes if it is watched continuously. This makes it sound like its conscious or something. There's no paradox here. "Watching" is just a series of measurements. Measurements collapse a state into an eigenstate. If you perform these frequently enough, the system doesn't have time to decohere, so it just keeps collapsing into the same eigenstate. It would be less like watching the pot and more like pulling it off the stove each time its about to boil. Anyway, I sound nitpicky, but I remember that before I learned QM I was always bothered by the fact that people tried to make it sound mysterious and vague for some reason when its actually quite objective and concrete.
- anonymousDan 13y ago
  > This makes it sound like its conscious or something. There's no paradox here IANAP, but I don't quite get the intuition behind the difference here. I thought the whole point of decoherence is that the quantum superposition collapses into an eigenstate?
- _Adam 13y ago
  I've seen some explanations that make it seem like subjective recognition of a quantum system in superposition is what caused it to decohere. The word "observed" doesn't imply interaction (to the lay-person, at least), so a term like "interacted with" would make things much clearer.
hughes 13y ago
I wish I knew more about quantum physics. With most science-related articles, I know enough to be able to tell what's journalistic hype and what contains an element of truth. But with anything about quantum physics or quantum computing, I am completely at a loss as to whether the ideas presented are even real, never mind having a hope of understanding them.
- loup-vaillant 13y ago
  Here is an understandable and serious 40.000 feet bird's eye view of quantum physics: http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ Having reading it, I'm confident this post is crap. The abstract of the scientific article behind it looks much better, though.
  - Double_Cast 13y ago
    I started reading the sequence a while ago. I'm confident I understood everything, up until the dialogue between the aliens who split their brains. There were simply too many streams of consciousness for me to follow. At that point, I decided to quit and come back to it after a few months. I find that sometimes, looking at a problem with a fresh mind is enough to solve it instantly.
andy_ppp 13y ago
This article is very exciting, it almost makes you wonder if the universe is set up to keep adding new possibilities to how much information can in theory be processed by biological systems... e.g. the brain. Anyway if this research is true it's incredible that nature has worked out such a clever hack. I've not seen many other examples of biology using quantum states - given the article there must be quite a few I assume?
- vanderZwan 13y ago
  Well, some scientists propose that smell uses quantum physics: http://www.ted.com/talks/luca_turin_on_the_science_of_scent.html http://www.ted.com/talks/luca_turin_on_the_science_of_scent.... (as I understand, Luca Turin's explanation isn't complete either - again it's a mix of different systems) There's also the theory that birds detect magnetic fields through quantum effects: http://www.newscientist.com/article/mg19826544.000-do-birds-see-with-quantum-eyes.html http://www.newscientist.com/article/mg19826544.000-do-birds-... Actually, I wonder if it's a coincidence that both of these are sensors. I can't think of any other examples at the moment, but why would't life evolve to exploit quantum effects where it can?
  - sbirchall 13y ago
    Quantum Bees: http://discovermagazine.com/1997/nov/quantumhoneybees1263 http://discovermagazine.com/1997/nov/quantumhoneybees1263 I know it's Discover and probably total crap, but I just love the idea.
dchichkov 13y ago
I think this article is auto-generated or pseudoscience.

89 points by digisth 13y ago

This is actually interesting. If their theory is correct plants have essentially loss less and super fast way for photons to traverse a random network^1. 1: They claim it is random network, I am not sure if we can call specific protein truly random. There is also question of size, scale of this effect might be small enough that there will be no applicable technology that could utilize it yet.

VladRussian2 13y ago
in the original article they clear that it isn't a photon, it is exciton that does the traveling: http://arxiv.org/pdf/1311.4688v1.pdf http://arxiv.org/pdf/1311.4688v1.pdf "In these systems excitons initiated by the incoming photons should travel really fast throughout a chain of chromophores in order to reach the reaction center where they are converted to chemical energy." >loss less and super fast way for photons to traverse a random network^1. My understanding is it isn't exactly loss less. It is a trade-off. The "natural" QM way of simultaneous multi-path travel is the super fast way of finding the reaction center. The issue is that many of these multi-paths may interfere and as result some degree of "entrapment" happens significantly delaying the arrival at the reaction center (Anderson localization - on a lattice draw all possible ways from A to B, including loops, etc... and whenever paths pass through the same edge with different direction double the edge time on each path and given lattice complex enough the propagation would almost stall - very-very rough illustration). To minimize the delay, the nature seems to came up with workaround - [slightly] breaking the phases on different paths and it seems that coherence is still preserved so we still have multi-path simultaneity while the above mentioned Anderson localization is decreased because of phase mismatch. This phase breaking is result of interaction which causes some energy loss/dissipation.

deleted 13y ago

[deleted]

jheriko 13y ago

the writing smacks of pseudoscience sadly... the idea of 'a mix of quantum and classical' implies a lack of understanding of what quantum mechanics is and specifically the correspondence principle. when did these two things become separate in anything other than some categorisation of our theoretical understanding of things? The entire article is coloured with it which makes it hard to glean any valuable information from. The analogy (?) about light bouncing around proteins, superpositions and collapses is especially confusing. If you look at the paper it does seem genuine and without the hype and bad analogies. (although there is some quite bad grammar, and i am far enough from subjects i am comfortable with that this could be psuedoscience). What I get from this is 'we have done work on a very specific example of quantum computing in nature - that work provides evidence that such approaches are viable'

Xcelerate 13y ago

This is a really cool article! I've never heard of plants doing something like this. However, the article is written kind of sloppily. > Quantum states are highly fragile — sneeze and they disappear in a puff of smoke. No, quantum states never disappear. They just evolve in time. However, it is hard to isolate a system that you are assigning a state vector from its surroundings. > They say the processes behind light harvesting are a special blend of the quantum and the classical. This kind of misleadingly suggests that reality has separate quantum and classical components. That's not the case; everything is quantum. It's just that some things that occur cannot be described accurately with classical physics. > Because energy can exist in a superposition of states, it can travel a variety of routes around the network at the same time. And when it finds the correct destination, the superposition collapses, leaving the energy at the reaction centre. Light travels. Energy is just a number that's conserved in non-relativistic QM. Also, while I suppose you could describe light as traveling through every path at once (and I know a lot of physicists like to describe it this way too), it sounds much more mysterious than it needs to be to me. I would just say: "as the wavefunction evolves in time, its probability amplitude spreads throughout space". > Another is the quantum zeno effect, the paradoxical phenomenon in which an unstable state never changes if it is watched continuously. This makes it sound like its conscious or something. There's no paradox here. "Watching" is just a series of measurements. Measurements collapse a state into an eigenstate. If you perform these frequently enough, the system doesn't have time to decohere, so it just keeps collapsing into the same eigenstate. It would be less like watching the pot and more like pulling it off the stove each time its about to boil. Anyway, I sound nitpicky, but I remember that before I learned QM I was always bothered by the fact that people tried to make it sound mysterious and vague for some reason when its actually quite objective and concrete.

anonymousDan 13y ago
> This makes it sound like its conscious or something. There's no paradox here IANAP, but I don't quite get the intuition behind the difference here. I thought the whole point of decoherence is that the quantum superposition collapses into an eigenstate?
_Adam 13y ago
I've seen some explanations that make it seem like subjective recognition of a quantum system in superposition is what caused it to decohere. The word "observed" doesn't imply interaction (to the lay-person, at least), so a term like "interacted with" would make things much clearer.

hughes 13y ago

I wish I knew more about quantum physics. With most science-related articles, I know enough to be able to tell what's journalistic hype and what contains an element of truth. But with anything about quantum physics or quantum computing, I am completely at a loss as to whether the ideas presented are even real, never mind having a hope of understanding them.

loup-vaillant 13y ago
Here is an understandable and serious 40.000 feet bird's eye view of quantum physics: http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ Having reading it, I'm confident this post is crap. The abstract of the scientific article behind it looks much better, though.
- Double_Cast 13y ago
  I started reading the sequence a while ago. I'm confident I understood everything, up until the dialogue between the aliens who split their brains. There were simply too many streams of consciousness for me to follow. At that point, I decided to quit and come back to it after a few months. I find that sometimes, looking at a problem with a fresh mind is enough to solve it instantly.

andy_ppp 13y ago

This article is very exciting, it almost makes you wonder if the universe is set up to keep adding new possibilities to how much information can in theory be processed by biological systems... e.g. the brain. Anyway if this research is true it's incredible that nature has worked out such a clever hack. I've not seen many other examples of biology using quantum states - given the article there must be quite a few I assume?

vanderZwan 13y ago
Well, some scientists propose that smell uses quantum physics: http://www.ted.com/talks/luca_turin_on_the_science_of_scent.html http://www.ted.com/talks/luca_turin_on_the_science_of_scent.... (as I understand, Luca Turin's explanation isn't complete either - again it's a mix of different systems) There's also the theory that birds detect magnetic fields through quantum effects: http://www.newscientist.com/article/mg19826544.000-do-birds-see-with-quantum-eyes.html http://www.newscientist.com/article/mg19826544.000-do-birds-... Actually, I wonder if it's a coincidence that both of these are sensors. I can't think of any other examples at the moment, but why would't life evolve to exploit quantum effects where it can?
- sbirchall 13y ago
  Quantum Bees: http://discovermagazine.com/1997/nov/quantumhoneybees1263 http://discovermagazine.com/1997/nov/quantumhoneybees1263 I know it's Discover and probably total crap, but I just love the idea.

dchichkov 13y ago

I think this article is auto-generated or pseudoscience.