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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 hi

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.
gizmo686 13y ago
>Energy is just a number that's conserved in non-relativistic QM. What happens in relativistic QM?
- Xcelerate 13y ago
  It's not really conserved. Here's a better article about it than anything I could explain: http://motls.blogspot.com/2010/08/why-and-how-energy-is-not-conserved-in.html http://motls.blogspot.com/2010/08/why-and-how-energy-is-not-...
  - Double_Cast 13y ago
    ow... I tried reading, and largely failed. The only thing I got out of that was "Energy density of universe is conserved. universe is expanding. Therefore, total energy is increasing." But not sure if even that part is correct.
loup-vaillant 13y ago
My turn to nitpick: > as the wavefunction evolves in time, its probability amplitude spreads throughout space sed 's/probability//' Probability is a real number embodied in a state of mind[1]. Amplitude are (as far as current physics believes) a complex number out there in the world. I know, squared norm and Born statistics, but still.[2] http://lesswrong.com/lw/oj/probability_is_in_the_mind/ http://lesswrong.com/lw/oj/probability_is_in_the_mind/ http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ http://lesswrong.com/lw/r5/the_quantum_physics_sequence/
- darkmighty 13y ago
  Oh god who writes those? It's a convention in physics to call it probability amplitude because, you know, it makes sense, as a direct analogous to energy. (http://en.wikipedia.org/wiki/Probability_amplitude http://en.wikipedia.org/wiki/Probability_amplitude) If you want to learn quantum mechanics there are far better places than sketchy, hand waving articles. I'd start here: http://www.youtube.com/watch?v=hUJfjRoxCbk http://www.youtube.com/watch?v=hUJfjRoxCbk
  - loup-vaillant 13y ago
    > It's a convention in physics to call it probability amplitude because, you know, it makes sense, as a direct analogous to energy. Wait, what? Could you please flesh out the analogy between probability and energy? --- From the Wikipedia article: > Probability amplitudes provide a physical meaning of the wave function, a link first proposed by Max Born, and this is a pillar of the Copenhagen interpretation of quantum mechanics. Oh, my… I'd say the real pillar of the Copenhagen interpretation is the word "probability". Which is rather weak, compared to the fact that the collapse postulate of the Copenhagen interpretation is non-linear, non-unitary, non-differentiable (even discontinuous!), non-local, violates CPT-symmetry and Liouville's Theorem, non-deterministic, and faster-than-light. Oh, and it's strictly more complex than a many-world interpretation, since it adds an extra postulate on top of existing equations. http://lesswrong.com/lw/q6/collapse_postulates/ http://lesswrong.com/lw/q6/collapse_postulates/ Seriously, how many arrows to the chest does the Copenhagen Interpretation must endure before we declare it dead, and stop saying "probability" before every occurrence of "amplitude"? --- Fire a photon through a half sieved mirror, with 2 sensors to catch the 2 possible paths, such that no matter what, one of the sensors will go off. What do you think happens? The equations (you know them more than I do) say the amplitude will flow and decohere into 2 non-interacting blobs. The blob where sensor 1 goes off, and the blob where sensor 2 goes off. (Note from Captain Obvious: the equations are deterministic. They do not say that God plays dice with the universe.) Now say you fire the photon, and observe sensor 1 going off. What do you think happened to the other blob, the one you don't interact with? Do you think it went away just like that? It would be like believing that a colonization spaceship going beyond the observable universe disappears, not only from your view, but for good. http://lesswrong.com/lw/pb/belief_in_the_implied_invisible/ http://lesswrong.com/lw/pb/belief_in_the_implied_invisible/ --- Of course this sequence is sketchy and hand waving (it doesn't even try to hide it). Its purpose is not to teach us Quantum Physics. Only certain aspects of it, to serve a philosophical agenda (most notably questions around personal identity and Free Will).
joe_the_user 13y ago
Oh God, Your post seems like nothing but that "genre" of hn post someone pointed out recently. It's the "let me show you I'm smart by pointing the article is technically incorrect in how it states things even though its statements are how both informed laymen and experts tend to express thing" Post OK, for "Quantum state", substitute "states requiring a specifically probabilistic/quantum-mechanical description" and for "classical states" substitute states amenable to a classical description. And someone else can explain the other things for you if you need it.
- Xcelerate 13y ago
  > Your post seems like nothing but that "genre" of hn post someone pointed out recently. Yeah, sorry about that. I was kind of worried it would come across that way. I was just thinking though of what kind of clarifications I would have liked to have had with this kind of article before I knew anything about the subject and thought some others might as well.
  - sbirchall 13y ago
    I think you added something to the conversation, and being the top comment it would seem so do other users. The comment made by 'joe_the_user, however, is shallow and pointless and advances the conversation in no direction but down. I think it's often good to have someone point out the "editorialisation" (for want of a better word) of an article, because after all this material has been designed for (somewhat) casual consumption, not as a how-to. But we're hackers and we like to start sentences with the word "Technically..." ;)
yetanotherphd 13y ago
It would be better if for each statement, you said how it should have been phrased rather than just why you thought it was wrong. My opinion is that you really are nitpicking, in the sense that the author is making the best explanation possible, but you wouldn't accept any verbal explanation.
aniijbod 13y ago
This is a very interesting comment indeed. I am far too poorly informed to be able to tell if anything you say here is reasonable, but I must admit that your comments all sound very reasonable. But lets please get instead to the substance of the article that you are commenting upon: tell us more about what do you think regarding the implications of the central claims of the article itself?

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.

gizmo686 13y ago

>Energy is just a number that's conserved in non-relativistic QM. What happens in relativistic QM?

Xcelerate 13y ago
It's not really conserved. Here's a better article about it than anything I could explain: http://motls.blogspot.com/2010/08/why-and-how-energy-is-not-conserved-in.html http://motls.blogspot.com/2010/08/why-and-how-energy-is-not-...
- Double_Cast 13y ago
  ow... I tried reading, and largely failed. The only thing I got out of that was "Energy density of universe is conserved. universe is expanding. Therefore, total energy is increasing." But not sure if even that part is correct.

loup-vaillant 13y ago

My turn to nitpick: > as the wavefunction evolves in time, its probability amplitude spreads throughout space sed 's/probability//' Probability is a real number embodied in a state of mind[1]. Amplitude are (as far as current physics believes) a complex number out there in the world. I know, squared norm and Born statistics, but still.[2] http://lesswrong.com/lw/oj/probability_is_in_the_mind/ http://lesswrong.com/lw/oj/probability_is_in_the_mind/ http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ http://lesswrong.com/lw/r5/the_quantum_physics_sequence/

darkmighty 13y ago
Oh god who writes those? It's a convention in physics to call it probability amplitude because, you know, it makes sense, as a direct analogous to energy. (http://en.wikipedia.org/wiki/Probability_amplitude http://en.wikipedia.org/wiki/Probability_amplitude) If you want to learn quantum mechanics there are far better places than sketchy, hand waving articles. I'd start here: http://www.youtube.com/watch?v=hUJfjRoxCbk http://www.youtube.com/watch?v=hUJfjRoxCbk
- loup-vaillant 13y ago
  > It's a convention in physics to call it probability amplitude because, you know, it makes sense, as a direct analogous to energy. Wait, what? Could you please flesh out the analogy between probability and energy? --- From the Wikipedia article: > Probability amplitudes provide a physical meaning of the wave function, a link first proposed by Max Born, and this is a pillar of the Copenhagen interpretation of quantum mechanics. Oh, my… I'd say the real pillar of the Copenhagen interpretation is the word "probability". Which is rather weak, compared to the fact that the collapse postulate of the Copenhagen interpretation is non-linear, non-unitary, non-differentiable (even discontinuous!), non-local, violates CPT-symmetry and Liouville's Theorem, non-deterministic, and faster-than-light. Oh, and it's strictly more complex than a many-world interpretation, since it adds an extra postulate on top of existing equations. http://lesswrong.com/lw/q6/collapse_postulates/ http://lesswrong.com/lw/q6/collapse_postulates/ Seriously, how many arrows to the chest does the Copenhagen Interpretation must endure before we declare it dead, and stop saying "probability" before every occurrence of "amplitude"? --- Fire a photon through a half sieved mirror, with 2 sensors to catch the 2 possible paths, such that no matter what, one of the sensors will go off. What do you think happens? The equations (you know them more than I do) say the amplitude will flow and decohere into 2 non-interacting blobs. The blob where sensor 1 goes off, and the blob where sensor 2 goes off. (Note from Captain Obvious: the equations are deterministic. They do not say that God plays dice with the universe.) Now say you fire the photon, and observe sensor 1 going off. What do you think happened to the other blob, the one you don't interact with? Do you think it went away just like that? It would be like believing that a colonization spaceship going beyond the observable universe disappears, not only from your view, but for good. http://lesswrong.com/lw/pb/belief_in_the_implied_invisible/ http://lesswrong.com/lw/pb/belief_in_the_implied_invisible/ --- Of course this sequence is sketchy and hand waving (it doesn't even try to hide it). Its purpose is not to teach us Quantum Physics. Only certain aspects of it, to serve a philosophical agenda (most notably questions around personal identity and Free Will).

joe_the_user 13y ago

Oh God, Your post seems like nothing but that "genre" of hn post someone pointed out recently. It's the "let me show you I'm smart by pointing the article is technically incorrect in how it states things even though its statements are how both informed laymen and experts tend to express thing" Post OK, for "Quantum state", substitute "states requiring a specifically probabilistic/quantum-mechanical description" and for "classical states" substitute states amenable to a classical description. And someone else can explain the other things for you if you need it.

Xcelerate 13y ago
> Your post seems like nothing but that "genre" of hn post someone pointed out recently. Yeah, sorry about that. I was kind of worried it would come across that way. I was just thinking though of what kind of clarifications I would have liked to have had with this kind of article before I knew anything about the subject and thought some others might as well.
- sbirchall 13y ago
  I think you added something to the conversation, and being the top comment it would seem so do other users. The comment made by 'joe_the_user, however, is shallow and pointless and advances the conversation in no direction but down. I think it's often good to have someone point out the "editorialisation" (for want of a better word) of an article, because after all this material has been designed for (somewhat) casual consumption, not as a how-to. But we're hackers and we like to start sentences with the word "Technically..." ;)

yetanotherphd 13y ago

It would be better if for each statement, you said how it should have been phrased rather than just why you thought it was wrong. My opinion is that you really are nitpicking, in the sense that the author is making the best explanation possible, but you wouldn't accept any verbal explanation.

aniijbod 13y ago

This is a very interesting comment indeed. I am far too poorly informed to be able to tell if anything you say here is reasonable, but I must admit that your comments all sound very reasonable. But lets please get instead to the substance of the article that you are commenting upon: tell us more about what do you think regarding the implications of the central claims of the article itself?