Timeline for Why does the expectation value in quantum mechanics correspond to the classically measured value?
Current License: CC BY-SA 4.0
7 events
| when toggle format | what | by | license | comment | |
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| Jan 9, 2023 at 6:01 | comment | added | Roger V. | @JuanPerez what I am talking about here is the correspondence principle. | |
| Jan 8, 2023 at 19:53 | comment | added | Juan Perez | Classical physics is not a limiting case of quantum physics, at least not to our current knowledge. It should be, but we can't actually prove it with our theories. This inability is called "the measurement problem". | |
| Sep 26, 2022 at 12:47 | comment | added | Roger V. | @untreated_paramediensis_karnik strictly speaking, Ehrefest theorem is for position and momentum, but your example is interesting. Can we call Stern-Gerlach a classical measurement? Is there spin in classical limit? I think no... but I am curious to hear your line on this. | |
| Sep 26, 2022 at 12:40 | comment | added | untreated_paramediensis_karnik | My point is that when you perform a stern gerlach experiment, you measure either spin down or up, not the expectation value, which could be zero spin, I guess. I don't understand what is wrong with this line of thought. | |
| Sep 26, 2022 at 9:38 | comment | added | Roger V. | @untreated_paramediensis_karnik How do you deal with the fact that expectation values for many systems don't match any eigenvalue. I am not dealing with it (that is I am not expressing any opinions/original ideas) - quantum mechanics does, more precisely in this case the Ehrenfest theorem - what we measure classically is an average, not an eigenvalue. What might mislead you is that in QM one talks a lot about quantum measurement (wave function collapse, etc.) But what the Ehrenfest theorem deals with is really a more mundane problem - the limited precision. | |
| Sep 26, 2022 at 9:27 | comment | added | untreated_paramediensis_karnik | How do you deal with the fact that expectation values for many systems don't match any eigenvalue. Eigenvalues are the energies that are supposed to be measured, not expectation values.? | |
| Sep 24, 2022 at 13:37 | history | answered | Roger V. | CC BY-SA 4.0 |