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> “Its radically new approach paved the way for a greater understanding, that methods and concepts of classical physics could not be carried over in a future qu

> “Its radically new approach paved the way for a greater understanding, that methods and concepts of classical physics could not be carried over in a future quantum mechanics.” This is incorrect. The Hamiltonian in both statistical and quantum mechanics has the same basic structure. Quantization is the only real difference, but the other methods and concepts are structurally the same. > It was also a crucial factor in Heisenberg’s argument that the probabilistic character of his matrix mechanics (and also of Schrödinger’s 1926 version of quantum mechanics, called wave mechanics) couldn’t be explained away as a statistical expression of our ignorance about the details, as it is in classical statistical mechanics. Too bad that's an incorrect inference. Bohmian mechanics proves that this inference is incorrect, and it's not the only possibility either.

bowsamic 2y ago
Quantisation is a pretty big difference: it turns the observables into completely different mathematical objects. Also the Hamiltonian itself only has the same form as in classical physics if at most quadratic in the canonical variables
- whatshisface 2y ago
  The parent commenter was talking about Von Neumann mechanics.
  - bowsamic 2y ago
    That makes no difference
fao_ 2y ago
I'm sorry but I think I'm going to believe the man who wrote the article, who is an editor of Nature and has a Physics PhD[1], over someone who has made it their life's work to argue against established scientists on a website for Venture Capitalists :) [1]: https://en.wikipedia.org/wiki/Philip_Ball https://en.wikipedia.org/wiki/Philip_Ball
- whatshisface 2y ago
  Would you believe two? :-) Bohmian mechanics describes a classical pseudo random number generator that deterministically decides the outcome of quantum measurements, using instant communication between measurements so that conditional probability works. The modern rejection of classical uncertainty as an interpretation of quantum uncertainty stems from Bell's theorem, which shows that any model that achieves a similar philosophical goal as Bohmian mechanics has a similarly dissatisfactory reliance on instant communication. People of Heisenberg's generation had the right intuitions and were guessing in the right directions but they did not know Bell's theorem, or even that it was a worthwhile question.
  - jostylr 2y ago
    EPR demonstrated that if you insist on locality and experiments having results in accordance with quantum predictions, then there must be pre-existing elements of reality that determine the results. Bell demonstrated that pre-existing elements of reality and the quantum results of experiments are incompatible with locality. The two together imply that if you assume experiments have results when we say they do in the way quantum mechanics predicts, then there is something nonlocal going on. Hidden variable theories do not add to nor remove the problem of non locality though Bohmian mechanics makes it very clear what the mechanism is. Many worlds gets around this since experiments do not have definite results in that theory. Instead, the experimenter splits into multiple copies, each of which thinks there is a result of the experiment, but that is an illusion.
    - moi2388 2y ago
      No, that is only the case if you assume the experimenter is free to choose the experiment. Bell shows that in that case either locality or realism is violated. However, there is a simpler explanation, namely superdeterminism. You are in fact not free to choose the experiment, this choice also has physical causes.
- naasking 2y ago
  If you look at polls of physicists over the past few decades, many believed that Von Neumann's proof ruled out all hidden variable theories. This was wrong. Many others also believed that Bell's theorem ruled out hidden variable theories. This was also wrong, and Bell himself was actually a fan of Bohmian mechanics, which is a non-local hidden variable theory, and one of his motivations for deriving his famous theorem. All of this is to say that being a physicist doesn't make you an expert in quantum foundations. Neither am I, but I've read a diversity of literature from experts that work on quantum foundations, so I am aware of the range of misconceptions on this.

bowsamic 2y ago

Quantisation is a pretty big difference: it turns the observables into completely different mathematical objects. Also the Hamiltonian itself only has the same form as in classical physics if at most quadratic in the canonical variables

whatshisface 2y ago
The parent commenter was talking about Von Neumann mechanics.
- bowsamic 2y ago
  That makes no difference

fao_ 2y ago

I'm sorry but I think I'm going to believe the man who wrote the article, who is an editor of Nature and has a Physics PhD[1], over someone who has made it their life's work to argue against established scientists on a website for Venture Capitalists :) [1]: https://en.wikipedia.org/wiki/Philip_Ball https://en.wikipedia.org/wiki/Philip_Ball

whatshisface 2y ago
Would you believe two? :-) Bohmian mechanics describes a classical pseudo random number generator that deterministically decides the outcome of quantum measurements, using instant communication between measurements so that conditional probability works. The modern rejection of classical uncertainty as an interpretation of quantum uncertainty stems from Bell's theorem, which shows that any model that achieves a similar philosophical goal as Bohmian mechanics has a similarly dissatisfactory reliance on instant communication. People of Heisenberg's generation had the right intuitions and were guessing in the right directions but they did not know Bell's theorem, or even that it was a worthwhile question.
- jostylr 2y ago
  EPR demonstrated that if you insist on locality and experiments having results in accordance with quantum predictions, then there must be pre-existing elements of reality that determine the results. Bell demonstrated that pre-existing elements of reality and the quantum results of experiments are incompatible with locality. The two together imply that if you assume experiments have results when we say they do in the way quantum mechanics predicts, then there is something nonlocal going on. Hidden variable theories do not add to nor remove the problem of non locality though Bohmian mechanics makes it very clear what the mechanism is. Many worlds gets around this since experiments do not have definite results in that theory. Instead, the experimenter splits into multiple copies, each of which thinks there is a result of the experiment, but that is an illusion.
  - moi2388 2y ago
    No, that is only the case if you assume the experimenter is free to choose the experiment. Bell shows that in that case either locality or realism is violated. However, there is a simpler explanation, namely superdeterminism. You are in fact not free to choose the experiment, this choice also has physical causes.
naasking 2y ago
If you look at polls of physicists over the past few decades, many believed that Von Neumann's proof ruled out all hidden variable theories. This was wrong. Many others also believed that Bell's theorem ruled out hidden variable theories. This was also wrong, and Bell himself was actually a fan of Bohmian mechanics, which is a non-local hidden variable theory, and one of his motivations for deriving his famous theorem. All of this is to say that being a physicist doesn't make you an expert in quantum foundations. Neither am I, but I've read a diversity of literature from experts that work on quantum foundations, so I am aware of the range of misconceptions on this.