B Is Simulation Theory the Key to Understanding Quantum Mechanics?

[kurt101]

There is no spooky action at a distance in QM.

To really understand this, its one of the myths of QM promulgated in popularizations, you need to go back to Bell's original paper:
https://hal.archives-ouvertes.fr/jpa-00220688/document

I read the paper written by Bell. https://hal.archives-ouvertes.fr/jpa-00220688/document

First off, I am very familiar with and accept the conclusions of Bell's paper which I would characterize as there is a spooky correlation at a distance. A long time ago, when I was first learning about QM I was not convinced, but I am now and have been for a while now. So no need to convince me on this point!

In this paper Bell writes "Could we not be a little more clever, and devise a model which reproduces the quantum formulae completely ? No. It cannot be done, so long as action at a distance is excluded." So here Bell leaves open the possibility of action at a distance.

Near the end of his paper Bell addresses this issue specifically: "Thirdly, it may be that we have to admit that causal influences - do go faster than light. The role of Lorentz invariance in the completed theory would then be very problematic." And he concludes this paragraph with "The exact elucidation of concepts like 'message' and 'we', would be a formidable challenge." So from these remarks I got that action at a distance is "problematic" and "formidable" and there is nothing from Bell refuting the idea of action at a distance.

At the beginning of the paper, Bell discusses the behavior of the Stern-Gerlach device which for spin 1/2 particles gives you 2 clumps rather than the naïve classical expectation of a continuous distribution. He goes on to say:
"Phenomena of this kind /3/ made physicists despair of finding any consistent space-time picture of what goes on the atomic and subatomic scale. Making a virtue of necessity, and influenced by positivistic and instrumentalist philosophies /4/, many came to hold not only that it is difficult to find a coherent picture but that it is wrong to look for one - if not actually immoral then certainly unprofessional."

I found the discussion of the Stern-Gerlach device interesting and most challenging to the idea that QM could be deterministically simulated. The paper suggested some naïve strawmen models, but there was nothing in it refuting the idea. That being said, I think simulating the Stern-Gerlach and being able to reproduce the results of QM using an algorithm similar to the entanglement collapse algorithm used for EPR with photons is a good challenge. By the entanglement collapse algorithm I am referring to the one that myself, Boing3000, and Mentz114 have posted on this forum where the result of the first interaction resolves to the particle that has not yet interacted.

I also think that QM Born rule and the simulated entanglement collapse algorithm have to be saying the same thing for the algorithm to be meaningful. I am still working on understanding how the Born rule relates to probability. Hopefully the next paper on probability theory will help with this. So I will go on to read https://arxiv.org/abs/1402.6562 next.

 

[Mentz114]

I read the paper written by Bell. https://hal.archives-ouvertes.fr/jpa-00220688/document
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I also think that QM Born rule and the simulated entanglement collapse algorithm have to be saying the same thing for the algorithm to be meaningful. I am still working on understanding how the Born rule relates to probability. Hopefully the next paper on probability theory will help with this. So I will go on to read https://arxiv.org/abs/1402.6562 next.

The simulation proves nothing but it reinforces that one cannot use a separable probability distribution in the prediction $P(xy|\alpha\beta)$ and reproduce the QT predictions. We need at least $P(xy|\alpha\beta)=\tfrac{1}{2}\left[P(x|\alpha)P(y|\alpha\beta) + P(y|\beta)P(x|\alpha\beta)\right]$ which leads to $P(00|\alpha\beta) + P(11|\alpha\beta) = \cos(\alpha-\beta)^2$

 

[kurt101]

The simulation proves nothing but it reinforces that one cannot use a separable probability distribution in the prediction $P(xy|\alpha\beta)$ and reproduce the QT predictions. We need at least $P(xy|\alpha\beta)=\tfrac{1}{2}\left[P(x|\alpha)P(y|\alpha\beta) + P(y|\beta)P(x|\alpha\beta)\right]$ which leads to $P(00|\alpha\beta) + P(11|\alpha\beta) = \cos(\alpha-\beta)^2$

I am not sure what you mean by "The simulation proves nothing", but I want to explain why it is important and can prove or disprove much for me.

With my current knowledge of physics, the entanglement collapse algorithm (i.e. the simulation) is the only way I can rationalize the spooky correlation at a distance behavior with a model of the universe where particles are real in the sense that they mostly (minus the entanglement) have a distinct state. It is clear with entangled particles that when you take a distant action on one of the entangled particle groups, it impacts the result of what you measure on the other entangled particle group. The algorithm is a direct model of this observation when using photons. So for me proving the algorithm false or proving that it is not in any way compatible with QM theory means I likely have to abandon the idea of a particle mostly having a distinct state.

A particle not having a mostly distinct state is contrary to what we observe. Our model for a photon has a distinct energy and momentum and the formula for it is very simple. A photon has a distinct trajectory and it is predictable. The only part of a photon that is not predictable is when it interacts with something else and even then it has a degree of predictability (i.e. its polarization state is 100% predictable at orthogonal measurements). So it is definitely not irrational (at least with my knowledge) to think a photon has mostly distinct state.

If anyone who is knowledgeable on QM think this way of thinking is wrong, I would be interested in knowing the degree of certainty on this. And I don't mean being wrong on terminology stuff like using the term "action" versus "correlation" for describing what we observe, but on the idea that a particle has mostly a distinct state (minus entanglement) from the rest of the universe. Are we 100% certain the universe is not like this? For those who know with 100% certainty that this thinking is wrong, I would definitely appreciate a rational explanation, strong hint, or some idea of what I must learn to be 100% certain why this kind of thinking is wrong. Or is it the case that unlike say the result of Bell's theorem this area is still debated by experts?

 

[PeterDonis]

the entanglement collapse algorithm (i.e. the simulation)

What algorithm are you talking about? Are you talking about an algorithm that can reproduce the QM predictions? (And it has to in order to match experimental results.) Any such algorithm will not assign definite states to the individual particles; it only assigns a definite state to the whole system.

A particle not having a mostly distinct state is contrary to what we observe.

Why? We don't observe individual particles. We observe macroscopic effects that we attribute to "particles"--things like detectors clicking or bright spots appearing on screens.

Our model for a photon has a distinct energy and momentum

No, it doesn't. You need to learn the actual model before you start making pronouncements about it.

A photon has a distinct trajectory and it is predictable.

Wrong. You need to learn the actual model before you start making pronouncements about it.

If anyone who is knowledgeable on QM think this way of thinking is wrong, I would be interested in knowing the degree of certainty on this.

You're not going to get an answer that will satisfy you in a "B" level thread, because the models themselves, and the concepts behind them, and the thousands of experiments that forced physicists to consider these highly counterintuitive models, are not understandable at the "B" level. You need to take the time to learn what the models actually say, and what the experiments are that have led to those models (hint: there are a lot more experiments than just EPR measurements on pairs of entangled particles). Then you will have the background to either answer the question yourself, or ask it at an "I" or "A" level where it can be given a proper discussion.

Thread closed.