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Comment by wills_forward | Hacker News Reader

This paper is basically statistical mechanics with a quantum veneer. Two major issues:

1. Scale: They're simulating just 13 qubits with QuTiP and making grand claims about quantum thermodynamics. The computational complexity they're glossing over here is astronomical. Anyone who's actually worked with quantum systems knows you can't just handwave away the scaling problems.

2. Measurement Problem: Their whole argument about instantaneous vs time-averaged measurements is just repackaging the quantum measurement problem without actually solving anything. They're doing the same philosophical shell game that every "breakthrough" quantum paper does by moving around where they put the observer and pretending they've discovered something profound.

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I disagree with you on both fronts.

1. The main underpinning of this article is the analytical theory they come up with independent of their simulation. The fact that it explains a few qubits well is exactly why this is interesting. If you were to scale up their model - a spin-1/2 ising model, you would effectively get a classical magnet, which is obviously well described by classical thermodynamics. It's in limit of small systems that quantum mechanics makes thermodynamics tricky.

2. Their time averaging is just to remove fluctuations in the state, not avoid the measurement problem. They're looking at time averages of the density matrix, which still yields a quantum object that will collapse upon measurement. And as their mathematical model points out, this can be true for arbitrary time averaging windows, the limits just change respectively as smaller time averages allow for larger fluctuations. There's nothing being swept under the rug here.

Quantum mechanics is statistical mechanics in the complex numbers.

Quantum mechanics is Markov chains in imaginary time.

Can you explain that?

State transitions are probabilistic and operators have complex coefficients.

State transitions are deterministic, it's only measurement that is probabilistic.

Even that is arguable. Subjective experience is probabilistic… kinda.

Do atoms decay deterministically?

I saw the best minds of my generation pithposting on hn.

Yes, aka. continuously. Interactions with larger systems makes it appear discontinuous.

As long as they are isolated, their state is a superposition of all possible states, and evolves determinsitically, with the amplitude of each of these "sub-states" evolving perfectly determinsitically. If you want to perform a measurement, you choose a possible decomposition of the superposition state and measure along that axis, and you'll get one of the values along that axis, with a probability that is the modulus of the square of the (complex) amplitude of that value.

https://en.m.wikipedia.org/wiki/Wick_rotation

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