The Zen anti-interpretation of quantum mechanics (2021) • Hacker News Board

Re: The Zen anti-interpretation of quantum mechanics (2021)

#81

Post by AgentME » Wed, Dec 28, 2022, 3:10 AM UTC

kahnclusions wrote: post #61

goatlover wrote: post #31

Earlier quoted context omitted.

So you’re endorsing Many Worlds with an appeal to the anthropic principle. That’s fine, but you do have to assume MWI is the true interpretation of the mathematical formalism.

I’m not a fan of Many Worlds. Communication or even detection of the split universes is impossible, which means it is impossible to measure. And science requires measurement to confirm our theories. Which means the MWI is equivalent to a simpler interpretation that doesn’t require split universes.

If something moves far enough away from us that it exits our observable universe, should we assume it still exists, or that physics has a special collapse rule that makes it stop existing at that point? Just like the split universes, it's impossible to directly measure the existence of objects outside of our observable universe.

Re: The Zen anti-interpretation of quantum mechanics (2021)

#82

Post by consilient » Wed, Dec 28, 2022, 3:13 AM UTC

dools wrote: post #68

krastanov wrote: post #20

Earlier quoted context omitted.

For many people the statement "electromagnetic fields exist as a (fundamental) building block of Nature" is just as reasonable as "atoms exist as a (fundamental) building block of Nature". The word "fundamental" is not particularly important, I am keeping it for historical reasons. You are perfectly comfortable with the existence of atoms (given your comments about understanding sound waves), presumably because you k…

> what in your personal aesthetic tastes is making atoms more palatable? It’s pretty easy for me to imagine things bumping into each other because I see that happening all around me

Atoms aren't anything like that though. There are no little billiard balls, probability densities don't "bump", electrons don't actually orbit, and so on. Atoms just are what they are, and what they are does not admit a good "macrophysical analogy".

Re: The Zen anti-interpretation of quantum mechanics (2021)

#83

Post by burke » Wed, Dec 28, 2022, 3:13 AM UTC

kahnclusions wrote: post #61

goatlover wrote: post #31

Earlier quoted context omitted.

So you’re endorsing Many Worlds with an appeal to the anthropic principle. That’s fine, but you do have to assume MWI is the true interpretation of the mathematical formalism.

I’m not a fan of Many Worlds. Communication or even detection of the split universes is impossible, which means it is impossible to measure. And science requires measurement to confirm our theories. Which means the MWI is equivalent to a simpler interpretation that doesn’t require split universes.

> MWI is equivalent to a simpler interpretation that doesn’t require split universes.

That simpler interpretation is also equivalent to a simpler implementation that doesn’t require apparently-arbitrary resolutions of quantum probabilities (MWI). It’s essentially a question of where you hide the “weird”.

It seems likely to me that they’re both wrong, and the in-principle-untestability of all this points to our mental machinery just failing to map intuitive concepts onto this space, but I’m totally agnostic to this. I do find MWI more conceptually appealing.

Re: The Zen anti-interpretation of quantum mechanics (2021)

#84

Post by lmm » Wed, Dec 28, 2022, 3:15 AM UTC

goatlover wrote: post #53

DiogenesKynikos wrote: post #37

Earlier quoted context omitted.

The Many-Worlds Interpretation is not really an interpretation. It just says that the known laws of Quantum Mechanics are correct, and that any measurement process itself has to obey the laws of Quantum Mechanics. In other words, nothing un-Quantum-Mechanical happens during measurement.

It’s an interpretation because we don’t have any empirical evidence for the other worlds. Science requires evidence, math alone isn’t enough. MWI is metaphysics, which is fine. We all wax philosophical sometimes as humans. Even the great Feynman couldn’t help himself.

> It’s an interpretation because we don’t have any empirical evidence for the other worlds. Science requires evidence, math alone isn’t enough.

By that logic assuming that distant parts of the universe still exist is metaphysics (since it would take many years for any information from there to reach us), yet few people feel the need to call it such.

Re: The Zen anti-interpretation of quantum mechanics (2021)

#85

Post by consilient » Wed, Dec 28, 2022, 3:19 AM UTC

_0w8t wrote: post #79

pdonis wrote: post #63

Earlier quoted context omitted.

> There are attempts to explain the classical world using a notion of decoherence, but that have problems with little progress in the last, say, 20 years to address them. What problems? Note that Aaronson, in the article (as well as a number of commenters in the comments) gives decoherence as precisely the answer to the issue you raise.

One problem is the preferred basis. Why decoherence selects a particular basis? Another is that decoherence still does not explain the origin of probabilities. I.e. there are models that shows how a pure classical system may arise. But we still have no explanation how a classical device interacting with a quantum system gets the value it measures.

The preferred basis is (roughly) the eigenbasis for the interaction term between the thermal environment responsible for decoherence and the decohering system in question, since those are the states that are robust to thermal noise.

Outside the perturbative regime, there isn't a preferred basis because there aren't any classical observers.

Re: The Zen anti-interpretation of quantum mechanics (2021)

#86

Post by TedDoesntTalk » Wed, Dec 28, 2022, 3:21 AM UTC

consilient wrote: post #82

dools wrote: post #68

Earlier quoted context omitted.

> what in your personal aesthetic tastes is making atoms more palatable? It’s pretty easy for me to imagine things bumping into each other because I see that happening all around me

Atoms aren't anything like that though. There are no little billiard balls, probability densities don't "bump", electrons don't actually orbit, and so on. Atoms just are what they are, and what they are does not admit a good "macrophysical analogy".

> There are no little billiard balls … electrons don't actually orbit

Wait, what? What do they do then? My physical science education ended in high school.

Re: The Zen anti-interpretation of quantum mechanics (2021)

#87

Post by lmm » Wed, Dec 28, 2022, 3:32 AM UTC

Jensson wrote: post #49

layer8 wrote: post #44

Earlier quoted context omitted.

The perceived wave function collapse is explained by decoherence. There is no extra “split” that happens. “World” is just a term referring to the parts of the universal wave function that are entangled with each other. As to “exactly when the universe will split into many worlds”, it happens zillions of times per second pretty much everywhere. It’s even not clear whether the branching is a discrete and countable occu…

So when does decoherence happen? Provide a formula for it. That is what people struggle with in quantum mechanics, MWI just deflects the question. Without a formula for when this phenomena happens any "interpretation" is just nonsense, except as a tool to get towards that formula.

Decoherence of a system happens when the entropy of entanglement is maximal, so if you want a formula then it's S(Tr_a(p_ab)) -> N/e. In practice a complex system is probably never fully decoherent, but the separability is small enough to not matter; if we're being truly rigorous we work with it as a limit, similar to how we use the "classical limit" in other parts of QM or other contexts.

(Analogy: imagine saying "Relativity doesn't explain how we live in a Newtonian world. If relativity is valid, it should be able to say at exactly what speed motion becomes nonrelativistic. Provide a formula for it")

Re: The Zen anti-interpretation of quantum mechanics (2021)

#88

Post by lmm » Wed, Dec 28, 2022, 3:39 AM UTC

goatlover wrote: post #56

russdill wrote: post #46

Earlier quoted context omitted.

There isn't some physical event in MWI that splits worlds. It's just a consequence of decoherence.

But we only observe the cat being alive or dead. Where is the other cat? Are the many worlds hiding in the equation?

The other cat is being observed by the other you. When you open the box and look, you entangle your state with the cat's, and the wavefunction describing both of you becomes one that could be decomposed as a superposition of two "worlds", one with a live cat and a you who's observed a live cat, the other with a dead cat and a you who's observed a dead cat.

As far as I can see people's objection to this tends to be that they don't feel like they're in a superposition. To which my response is: what would you expect it to feel like? Bearing in mind that the wavefunction is describing all the states of your neurons etc..

Re: The Zen anti-interpretation of quantum mechanics (2021)

#89

Post by goatlover » Wed, Dec 28, 2022, 3:40 AM UTC

LightMachine wrote: post #74

criddell wrote: post #35

Earlier quoted context omitted.

> the correct mathematical models There are those that think reality (including the universe) is just mathematics. Not modeled by mathematics, but is mathematics. To me, the mathematical universe hypothesis is starting to be the only theory that makes sense.

Wait isn't that the common assumption? That the universe is just an algorithm and we're trying to figure which is it?

No, the common assumption is that we attempt to describe the universe with precise tools like mathematics, but the map isn’t the territory and all models are incomplete, some are just less incomplete. The universe being mathematical is a form of Platonism, which is the belief that mathematical and abstract objects are real.

Re: The Zen anti-interpretation of quantum mechanics (2021)

#90

Post by pdonis » Wed, Dec 28, 2022, 3:40 AM UTC

_0w8t wrote: post #79

pdonis wrote: post #63

Earlier quoted context omitted.

> There are attempts to explain the classical world using a notion of decoherence, but that have problems with little progress in the last, say, 20 years to address them. What problems? Note that Aaronson, in the article (as well as a number of commenters in the comments) gives decoherence as precisely the answer to the issue you raise.

One problem is the preferred basis. Why decoherence selects a particular basis? Another is that decoherence still does not explain the origin of probabilities. I.e. there are models that shows how a pure classical system may arise. But we still have no explanation how a classical device interacting with a quantum system gets the value it measures.

> Why decoherence selects a particular basis?

consilient answered this one.

> decoherence still does not explain the origin of probabilities

The amplitudes corresponding to each decoherent branch are the right ones to give the Born rule probabilities. Which, given that the Born rule is empirically observed to work, is probably as good as we're going to get unless (as I doubt will ever happen) someone manages to find a way to derive the Born rule from unitary dynamics.