Quantum Darwinism, an Idea to Explain Objective Reality, Passes First Tests(quantamagazine.org)
quantamagazine.org
Quantum Darwinism, an Idea to Explain Objective Reality, Passes First Tests
https://www.quantamagazine.org/quantum-darwinism-an-idea-to-explain-objective-reality-passes-first-tests-20190722/
43 comments
I was quoted in this piece, and adapted some of my correspondence with the author into a blog post: http://blog.jessriedel.com/2019/07/24/faq-about-experimental...
Are the actual papers available online? On arxiv.org?
Yes, they are linked from the blog post. The experimental papers are arXiv numbers 1803.01913, 1808.07388, and 1809.10456. The basic theoretical papers are available from the Wikipedia page on quantum Darwinism, also linked.
Ok, thanks!
I don't know if the analogy to darwinian evolution makes much sense, it seems to me that it makes more sense to see this as a way of error-correcting our reality, that is to say quantum phenomenon occur because anything else would cause a severe inconsistency.
It is indeed a stretch, but it's just supposed to be an evocative name not a perfect analogy. In particular, quantum Darwinism has a notion of fittest types of information, and this information is replicated, but it crucially does not feature a notion of mutation, so in particular it cannot result in increasing complexity/sophistication over time as produced by biological Darwinism.
Evocative "sorta" names have a tendency to spread misinformation when the scientific details are opaque to most people. It's not a practice that I think is okay.
Then you should probably express your displeasure to guy who picked the name :)
Seriously though, all evocative names are imperfect. Laymen always over interpret them. I don't like "quantum Darwinism" much, but if your standard is that the name of a mathematical concept not be misinterpreted, then basically all English words are out.
Seriously though, all evocative names are imperfect. Laymen always over interpret them. I don't like "quantum Darwinism" much, but if your standard is that the name of a mathematical concept not be misinterpreted, then basically all English words are out.
Relevant xkcd:
https://xkcd.com/895/
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Zurek explaining some of it @ https://www.youtube.com/watch?v=27zMdaBgt6g
Really good article but I’m unconvinced about those pointer states. The classicly observed values simply have overwhelmingly higher probability.
I also view the apearance of classical physics as you say, but I am not sure if that rules out this concept in the article. I admittedly don't really understand what the article is saying. (It takes me alot of work to understand these things.) The author does admit that this is just an implementation of the basic laws of quantum maechanics. I suppose why this is interesting is just that in large systems the aggregate behavior does not always follow obviously from the basic rules.
I would like to write down what I considered to be the standard motivation for why the classical solution arises, which is in other words why it is more probable, as you point out.
In the Feynman path integral formalism, any paths in the system is possible, with an amplitude proprotional to the exponential of the action. (Action as in a Lagrangian). For paths that are an extremum of the action, there is the least destructive interference between neighboring paths, since there is the smallest phase change between these neighboring paths. Of course this extremum of the action is, not coincidentally, the classical solution, which is the result from the lagrangian formulation of classical machanics.
I would like to write down what I considered to be the standard motivation for why the classical solution arises, which is in other words why it is more probable, as you point out.
In the Feynman path integral formalism, any paths in the system is possible, with an amplitude proprotional to the exponential of the action. (Action as in a Lagrangian). For paths that are an extremum of the action, there is the least destructive interference between neighboring paths, since there is the smallest phase change between these neighboring paths. Of course this extremum of the action is, not coincidentally, the classical solution, which is the result from the lagrangian formulation of classical machanics.
From the first paragraph of the article:
> An atom typically can’t be assigned a definite position, for example — we can merely calculate the probability of finding it in various places.
Is this really the case? Or maybe author meant 'electron' instead of 'atom'?
I mean, if we wouldn't be able of calculating the position of an Atom, how could "A Boy And His Atom" would be possible?
https://www.youtube.com/watch?v=oSCX78-8-q0
> An atom typically can’t be assigned a definite position, for example — we can merely calculate the probability of finding it in various places.
Is this really the case? Or maybe author meant 'electron' instead of 'atom'?
I mean, if we wouldn't be able of calculating the position of an Atom, how could "A Boy And His Atom" would be possible?
https://www.youtube.com/watch?v=oSCX78-8-q0
There is a limit to the precision of a position measurement of any particle, and atoms are made of many particles. The Heisenberg Uncertainty Principle states that the uncertainty of the position and momentum of a particle are related. In particular, the product of the errors has a constant lower bound. Visually, if you think of (1d) position and (1d) momentum plotted on a 2d graph, then Heisenberg's principle means that particles are not points, but rectangles with a minimum area.
I can tell when I don't truly understand something by my ability to disagree, or make counter arguments. In this case it sounds reasonable -- that the probability distributions of the quantum scale somehow cohere because of a Darwinian mechanism. But if you told me, oh, actually the center of mass of the probability distributions is perceived as the real location, that makes sense too.
I know it’s just an off the cuff example, but that one seems easy to argue against -- in the double slit experiment, the particle is perceived to go through both slits, not through the middle.
> possible only because pointer states of quantum objects exist
I knew it was pointers! So observation is the universe's GC? I feel better knowing that life is here at least to collapse enough wave functions to keep things humming along nicely. (Ever wake up and feel that you must have been stopped-and-copied over the night??)
I knew it was pointers! So observation is the universe's GC? I feel better knowing that life is here at least to collapse enough wave functions to keep things humming along nicely. (Ever wake up and feel that you must have been stopped-and-copied over the night??)
I know this is a joke, but QD specifically excludes the requirement of a living observer.
Wrap this up in an visualization animation and I'm sure I could understand it.
Here's a rebuttal from a physicist https://motls.blogspot.com/2019/07/quanta-magazines-anti-qua...
This rebuttal is very weak. It’s attacking straw men, not really addressing the original article at all.
For example, Motl objects to Ball’s The world we’re living in sure doesn’t feel quantum mechanical by quoting himself(!): some people keep on saying that it "looks like" there must be a classical mechanism beneath the quantum phenomena.
That’s a ludicrous misreading of the article. Ball isn’t claiming that nature is somehow secretly classical, he’s saying it is quantum but looks classical in everyday life. Ball is in fact making the same claim as Motl himself, if only Motl could see it.
Or for another example, Motl objects to Ball’s How do quantum probabilities coalesce into the sharp focus of the classical world? and insists that they do not in fact coalesce: Statements about big objects' properties may "look" certain because quantum mechanics may predict probabilities to be 99.9999% or higher [...] But quantum mechanics never allows the certainty to go to 100%
Again, Motl is in violent agreement with Ball! The whole thrust of the article is that wave function collapse is not a special process outside of known quantum mechanics, doesn’t depend on consciousness, and doesn’t require an observer. It’s a statistical process where the probability of seeing a singular, classical-like state will tend towards 1 as a system interacts with its environment and decoheres.
And there are plenty more such examples. It seems like Motl in fact agrees with the article, but objects to... the tone for some reason?
Or maybe he just thinks it’s trivial? If so, I don’t think that’s fair at all, as wave function collapse really is widely depicted as highly mysterious, in pop science circles at least.
For example, Motl objects to Ball’s The world we’re living in sure doesn’t feel quantum mechanical by quoting himself(!): some people keep on saying that it "looks like" there must be a classical mechanism beneath the quantum phenomena.
That’s a ludicrous misreading of the article. Ball isn’t claiming that nature is somehow secretly classical, he’s saying it is quantum but looks classical in everyday life. Ball is in fact making the same claim as Motl himself, if only Motl could see it.
Or for another example, Motl objects to Ball’s How do quantum probabilities coalesce into the sharp focus of the classical world? and insists that they do not in fact coalesce: Statements about big objects' properties may "look" certain because quantum mechanics may predict probabilities to be 99.9999% or higher [...] But quantum mechanics never allows the certainty to go to 100%
Again, Motl is in violent agreement with Ball! The whole thrust of the article is that wave function collapse is not a special process outside of known quantum mechanics, doesn’t depend on consciousness, and doesn’t require an observer. It’s a statistical process where the probability of seeing a singular, classical-like state will tend towards 1 as a system interacts with its environment and decoheres.
And there are plenty more such examples. It seems like Motl in fact agrees with the article, but objects to... the tone for some reason?
Or maybe he just thinks it’s trivial? If so, I don’t think that’s fair at all, as wave function collapse really is widely depicted as highly mysterious, in pop science circles at least.
The rebuttal takes a view which is close to my heart—but [Motl] puts it so viciously, dismisses without genuine inquiry or curiosity the intriguing claims of the article, and plays so much faster and looser with his ideas than the author he critiques—you can taste his contrition. Ball and [Motl] are probably both mistaken about what QD actually explains.
Edit: fixed names
Edit: fixed names
For future reference, "Luboš Motl" and "puts it so viciously, dismisses without genuine inquiry or curiosity [....], and plays so much faster and looser with his ideas than the author he critiques—you can taste his contrition" are pretty much synonymous. The man's a troll with a PhD.
Could you explain your view in a calmer and clearer way than Motl? I’m curious whether there’s any “there” there, so to speak.
QD as described in Ball’s article sounds very sensible to me, and Motl’s objections sound like he misunderstands the article and would actually mostly agree with QD.
QD as described in Ball’s article sounds very sensible to me, and Motl’s objections sound like he misunderstands the article and would actually mostly agree with QD.
(The author of the blog post is Luboš Motl. Pilsen is the name of a town in Czechia where he presumably lives.)
I sort of got this but I found this article full of clunky analogies including the "Darwinism" tag itself.
So much for parallel universes?
Damn I feel stupid.
Don't. I just got my PhD (working on quantum computing at a good school) and I do not really get the point they are making. It is interesting, but esoteric even for people working in related fields.
However, it is a great opportunity to start learning more about it!
However, it is a great opportunity to start learning more about it!
My comment isn't useful, but I really can't get a handle on anything "quantum" related. The only thing I sort of understand is that if you could entangle a massive amount of photons/electrons, you could have "quantum radar" which would be jam-proof.
I don't really understand even that though. Could you verify an electron reflecting back is entangled with an electron you have on hand, or are they all just "entangled" with something or "entangled" with some spin (which could be replicated)?
I don't really understand even that though. Could you verify an electron reflecting back is entangled with an electron you have on hand, or are they all just "entangled" with something or "entangled" with some spin (which could be replicated)?
>My comment isn't useful, but I really can't get a handle on anything "quantum" related.
That is probably because you have tried to read "applications" papers/articles (some of them of dubious scientific value, and more sci-fi/futurology) without properly understanding the fundamentals first. I strongly recommend "Quantum Mechanics", Cohen-Tannoudji et al. The first two chapters are the best introduction to quantum mechanics I've read: concise and to the point, starting from experiment and explaining the key ideas of quantum theory, and then the mathematical formulation.
That is probably because you have tried to read "applications" papers/articles (some of them of dubious scientific value, and more sci-fi/futurology) without properly understanding the fundamentals first. I strongly recommend "Quantum Mechanics", Cohen-Tannoudji et al. The first two chapters are the best introduction to quantum mechanics I've read: concise and to the point, starting from experiment and explaining the key ideas of quantum theory, and then the mathematical formulation.
Thanks for the recommendation!
This is a go-to resources for laymen who would like to learn the basics of physics. https://theoreticalminimum.com/
Thanks for that! Hadn’t come across this. Seems like the perfect way to refresh the knowledge I once had (bachelor degree 1986).
As a layman I just can't get past the glaring reality of: we simply do not possess the means (i.e. equipment/tools) to examine/measure/control the fundamental elements of matter without utterly affecting the outcome in ways we are not able to control, understand or accurately predict.
I don't believe there is any amount of quantum theories that will get us past this fundamental boundary.
I don't believe there is any amount of quantum theories that will get us past this fundamental boundary.
It can be made to work in at least some cases -- for example, QED is a theory about how individual photons and electrons behave that’s in truly fantastic agreement with experimental results.
There’s a deep philosophical question about whether we can every truly learn the real fundamental laws of nature, sure; but it certainly looks like we can get very very close, perhaps arbitrarily close.
There’s a deep philosophical question about whether we can every truly learn the real fundamental laws of nature, sure; but it certainly looks like we can get very very close, perhaps arbitrarily close.