Yes they are both particles and waves, but “collapse” is also purely a mathematical trick and isn’t something that physically occurs. Quantum theory is a statistical theory and like all statistical theories, you model the evolution of the system statistically up until it gets to the point you want to make a prediction for. But state vector notation (the “wave function”) is just a mathematical convenience that works when you are dealing with a system in a pure state that is only subject to Schrodinger evolution. It doesn’t work when a system undergoes decoherence, which follows the Born rule, and that says to compute the square magnitude of the state vector. But if you compute the square magnitude of the state vector, you get a new vector that is no longer a valid state vector.

Conveniently, whenever a system is subject to decoherence/Born evolution, that happens to be a situation when you can acquire new physical information about a system, whereas whenever it is subject to Schrodinger evolution, that corresponds to a situation when you cannot. People thus do this mathematical trick where, whenever a system undergoes decoherence/Born evolution, they take pause their statistical simulation, grab the new information provided about the system, and plug it back into the state vector, which allows them to reduce one probability amplitude to 1 and the rest to 0, which gives you a valid state vector again, and then they press play on their statistical simulation and carry it on from there.

This works, yes, but you can also pause a classical statistical simulation, grab new information from real-world measurements, and plug it in as well, unpause the simulation, and you would also see a sudden “jump” in the mathematics, but this is because you went around the statistical machinery itself into the real world to collect new information to plug into the computation. It doesn’t represent anything actually physically occurring to the system.

And, again, it’s ultimately just a mathematical trick because it’s easier to model a system in a pure state because you can model it with the state vector, but the state vector (the “wave function”) is simply not fundamental in quantum mechanics and this is a mistake people often make and get confused by. You can evolve a state vector according to Schrodinger evolution only as long as it is in a pure state, the moment decoherence/Born evolution gets involved, you cannot model it with the state vector anymore, and so people use this mathematical trick to basically hop over having to compute what happens during decoherence, and then delude themselves into thinking that this “hop” was something that happened in physical reality.

If you want to evolve a state vector according to the Schrodinger equation, you just compute U(t)ψ. But if you instead represent it in density matrix form, you would evolve it according to the Schrodinger equation by computing U(t)ψψᵗU(t)ᵗ. It obviously gets a lot more complicated, so in state vector form it is simpler than density matrix form, so people want to stick to state vector form, but state vector form simply cannot model decoherence/Born evolution, and so this requires you to carry out the “collapse” trick to maintain in that notation. If you instead just model the system in density matrix form, you don’t have to leave the statistical machinery with updates about real information from the real world midway through your calculations, you can keep computing the evolution of the statistics until the very end.

What you find is that the decoherence/Born evolution is not a sudden process but a continuous and linear process computed with the Kraus operators using ΣKᵢ(t)ρKᵢ(t)ᵗ and takes time to occur, cannot be faster than the quantum speed limit.

While particles can show up anywhere in the universe in quantum mechanics, that is corrected for in quantum field theory. A particle’s probability of showing up somewhere doesn’t extend beyond its light cone when you introduce relativistic constraints.

There is no way to “establish whether or not there is an objective reality.” It’s a philosophical position. You either take the reality which we observe and study as part of the material sciences to be objective reality, or you don’t believe it’s objective reality and think it is all sort of invented in the “mind” somehow. Either position you take, you cannot prove or disprove either one, because even if you take the latter position, no evidence I present to you could change your mind because to be presented evidence would only mean for that evidence to appear in the mind, and thus wouldn’t prove anything. The best argument we can make is just taking the reality we observe as indeed reality is just philosophically simpler, but that also requires you to philosophically value simplicity, which you cannot prove what philosophical principles we should value with science either.

There’s still a pattern in the results, so by one means or another we want to explain the results. Just calling it nondeterministic, if I understand right, would be just saying you can’t predict it from prior observations. So, whatever language you use to describe this puzzling situation, the puzzling situation thus far remains.

I mean nondeterministic in a more fundamental sense, that it is just genuinely random and there is no possibility of predicting the outcome because nothing in nature actually pre-determines the outcome.

A priori?

Through rigorous experimental observation, it’s probably the most well-tested finding in all of science of all time.

Or because it best fits with Relativity? It sounds about as strong as saying, “we know time is universal.” It’s obvious, has to be true, but apparently not how the universe functions.

So we can never believe anything? We might as well deny the earth is round because people once thought time is absolute now we know it’s relative, so we might as well not believe in anything at all! Completely and utterly absurd. You sound just like the creationists who try to undermine belief in scientific findings because “science is always changing,” as if that’s a bad thing or a reason to doubt it.

We should believe what the evidence shows us. We changed our mind about the nature of time because we discovered new evidence showing the previous intuition was wrong, not because some random dude on lemmy dot com decided their personal guesses are better than what the scientific evidence overwhelmingly demonstrates.

If you think it’s wrong show evidence that it is wrong. Don’t hit me with this sophistry BS and insult my intelligence. I do not appreciate it.

Maybe you are right that special relativity is wrong, but show me an experiment where Lorentz invariance is violated. Then I will take you seriously. Otherwise, I will not.

Quantum nonlocality really is a misnomer. Nothing is nonlocal about it. We know from the No-communication Theorem that there is no physical interaction you could carry out with one particle in an entangled pair that would affect the state of the other particle, and we know it is compatible with special relativity, which is a fundamentally local theory, as such a unification of the two is how we get quantum field theory.

“Local realism” is also a nonsensical term. There is no agreed upon rigorous definition of “realism” and its introduction to the scientific literature has only served to confuse the discussion and promote quantum mysticism because people think because Bell’s theorem supposedly shows that “local realism” is false that you there have to choose between locality or realism, but not both, and since we know the universe is local, we have to conclude there is no objective reality, devolving into mysticism and idealism.

This isn’t just a problem in popsci articles but even in published scientific literature. This “local realism” hogwash has caused even otherwise respectable physics to publish nonsense about how reality doesn’t exist. The term “realism” is never used in Bell’s theorem and has tn relevance to it. Bell’s theorem is about local hidden variable theories, and it is complete nonsense to conflate hidden variables with “realism” as if your only choices are to believe the reality is deterministic or to deny reality even exists! What kind of options are those? What about a third option that reality exists and it is just nondeterministic?

What Bell’s theorem shows is that quantum mechanics cannot be replaced with a local hidden variable theory, and since we know the universe is local, that means it cannot be replaced with a hidden variable theory. It forces us to accept nondeterminism, it doesn’t force us to deny reality, nor does it prove there is nonlocality.

It can, under certain conditions, contain information about things at a distance, but a function is not a physical entity and its reduction is not a physical process, so none of this reflects anything superluminal actually going on in physical reality.