Question

What is the quantum measurement problem? Explain one proposed solution to that problem, in under 2000 words.

Answer 1

“quantum measurement problem” is a not real "problem" which these authors say they offer a "physical way out of a mathematical embarrassment” to something that is certainly not an embarrassment. Instead quantum uncertainty is what nature tells us about what is and what we can know. They are reported to conclude that the "dynamical instabilities inside the apparatus near the end of the measurement." can permit the statistical outcomes without need for a physical collapse. But no collapse nor multiple universes are really needed at all. That gets to the point that QM is not classic physics and trying to make it that is not productive. The reporting is that:

"The statistical formulation of quantum mechanics, though abstract and minimalist, is sufficient to explain all relevant features. Since alternative interpretations involve unnecessary assumptions of one kind or another, the authors advocate the usage of the statistical formulation in physics education of quantum mechanics."

So their conclusion is correct but I don't get why they think they have added anything - that is unless somehow saying that some large collection of quantum states that we call a measuring device can form a meta-stable state that then does not collapse when an observation is made. Although it is controversial to say this it is I think most correct to say that there is no wave function collapse. there is no measurement problem. Uncertainty is inherent. QM requires that we give up usual notions of reality but it requires little beyond HS math to follow. The description of the wave function is a math language that best allows us to describe what nature allows us to predict or know. It has withstood all tests. It is absolutely clear that one cannot separate measurer and measured. It requires no collapse to provide it's answers and it tells us that we cannot know more than probabilistic outcomes for what we choose subjectively as observations

And the

If the work in question shows that there is no collapse but just the very quick evolution of the wave function into something that resembles collapse very closely whenever a large number of oscillators interact with something like an electron, then the problem is completely solved. I believe that that is what it shows but cannot prove it. No subjectivity is required for it to happen as the brain would work like the magnet they describe.

The reason we only observe the states we observe, presumably, is because the brain, like the measuring magnet they describe, goes through a similar process whenever it interacts with something like an electron, and it generates our consciousness in a way the reflects its own physical state, and since its physical "state" is as they describes and resembles a single "collapsed" - almost - quantum state and not a broader superposition then that's what we experience. They did their proof not of the brain but of a magnet but the importance of their paper is that presumably the same approach could be used for other physical systems composed of large numbers of oscillators.

So except in the extremely unlikely cases we will observe the states and not something that resembles superposition or rather we experience only superpositions that add up to a function that is almost certainly so close to the state that we can't tell the difference, and we can never measure with enough precision to know the difference. What we observe in the unlikely cases, or even if we observe and don't just die, or become unconscious for a while, is unanswered and probably will remain so because the probabilities of ever having it happen are so low and because it probably doesn't last long enough. It will take the finishing of David Chalmers program to decide all of that. Perhaps a step can now be made by associating experience with certain very high probabilities in the brain. Also, since the pseudo collapse occurs so quickly and the temporal resolution of our consciousness is so low then we don't actually see it happening.

In the future there may be sufficient control of the brain to sort of time lapse the pseudo-collapse and experience it, or else that is not possible as the un-pseudo-collapsed brain does not result in consciousness or slows consciousness down so an instant seems like a long time defeating the experiment.