Reality is a superposition of eigenstates. Even if we use the pilot-wave formalism, in which a particle has definite position or momentum, the pilot wave itself is in a superposition.
— Me@2012-04-16 2:27:20 PM
Physics reality is NOT a superposition of eigenstates. If physics reality was a superposition of eigenstates, there would have never been any interference patterns.
For an experimental setup, what is in a superposition is the quantum state, which is a tool for deducing probabilities of different potential measurement results.
“A quantum state is a superposition of eigenstates” just means nothing more than that we need to use individual probabilities of the eigenstates to calculate the probabilities.
A quantum state, which is represented by a wave function, is logical, mathematical, conceptual, and linguistic in nature. A quantum state is NOT physical. A quantum state is NOT reality. A quantum state is NOT directly corresponding to a physical reality (aka observable events, measurement results, etc.)
A quantum state is NOT even corresponding to a probability directly. (If a quantum state was a probability, there would have never been the phenomenon of interference.) Instead, a quantum state is corresponding to a probability amplitude, which is used for calculating probabilities.
From Personal Computer[s] to Personal Robots
In the beginning of the optical fiber research,
there were a lot of difficulties. But I thought if
[I succeeded], the research payoff would be huge,
because it could create a whole new world.
By the Father of Optical Fibers
Make Robot as inexpensive and as useful as
Personal Computer -- Personal Robot
2023.03.15 Wednesday (c) All rights reserved by ACHK
What happens in the interval between the initial and final states of the interaction process?
What happens in between is everything and nothing. There is no privileged clearcut answer what happened that would be physically meaningful. It’s really the very basic point of quantum mechanics that only results of measurements are physically meaningful facts or observables; all other data are fictitious or uncertain. By the very definition of your problem, no measurement took place in the intermediate states which means that no sharp answers to any questions were generated, no answers or values became real or privileged or facts.
But unlike classical physics, quantum mechanics says that not only the probabilities of each history matter. All the relative phases matter, too.
There was a really good chapter on his time in a biology lab in his book, “Surely you’re joking Mr. Feynman”. I have always remembered this quote:
When it came time for me to give my talk on the subject, I started off by drawing an outline of the cat and began to name the various muscles.
The other students in the class interrupt me: “We know all that!”
“Oh,” I say, “you do? Then no wonder I can catch up with you so fast after you’ve had four years of biology.” They had wasted all their time memorizing stuff like that, when it could be looked up in fifteen minutes.
sykh on May 15, 2018
Feynman was wrong on his view. The same thing could have been said of him and physicists. Oh, you spent your time memorizing formulas when it could be looked up in 15 minutes.
This is a nonsensical point of view for two reasons.  People in areas of their expertise tend to know a lot in that area off the top of their head because they have encountered this stuff so much that it has become memorized. That memorized knowledge comes from experience not a memorization exercise.  It’s also nonsensical because if you didn’t have a core set of knowledge memorized in your area of expertise and instead relied on spending 15 minutes looking up each fact necessary to understand a given situation you’d end up wasting your whole day just trying to understand the meaning of the problem.
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