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But how does the wavefunction become narrow and sharp "due to measurement?" That's the crux; that's what the measurement problem is. Making a wavefunction "nar

But how does the wavefunction become narrow and sharp "due to measurement?" That's the crux; that's what the measurement problem is. Making a wavefunction "narrow and sharp" means projecting it onto an eigenvector of your measurement basis (e.g. "spin up.") Projection is non-unitary and irreversible. Whether and how this can be achieved via the Schrodinger equation is what all the fuss is about.

scotty79 7y ago
Schrodinger equation describes evolution, but not reshaping. Reshaping is caused by interaction. Interaction occurs with probability defined by wave functions. The thing is, to predict results of experiments we don't really need to know how exactly wave function reshapes. It's enough to know how it "reshapes" to a specific point, that we from that moment on call a particle that came out of wavefunction collapse. You can consider as many points in as you need to calculate everything you want to know. Hence current state of quantum mechanics where we can calculate everythig but don't feel as we have a full picture of what happens.
- username90 7y ago
  Said reshaping is the hard part, basically everybody who have studied a bit of physics understands the schrödinger equation and the wave part, the hard part is the particle like behavior which causes the wave to break down. Meaning it isn't a wave, waves doesn't break down like that, waves doesn't just gather together into some coherent state randomly. That is the hard part, if you can't explain that then don't say that QM is easy.
- kgwgk 7y ago
  Many interactions are perfectly described by Schroedinger's equation. The interactions inside an atom, for example. Or the operation of a quantum computer. What "occurs" (that's the part we don't really understand) with probability defined by wave function is "measurement" but not every interaction is a measurement. A measurement is the macroscopic effect of interactions (which may or may not be fully described by Schroedinger's equation).

scotty79 7y ago

Schrodinger equation describes evolution, but not reshaping. Reshaping is caused by interaction. Interaction occurs with probability defined by wave functions. The thing is, to predict results of experiments we don't really need to know how exactly wave function reshapes. It's enough to know how it "reshapes" to a specific point, that we from that moment on call a particle that came out of wavefunction collapse. You can consider as many points in as you need to calculate everything you want to know. Hence current state of quantum mechanics where we can calculate everythig but don't feel as we have a full picture of what happens.

username90 7y ago
Said reshaping is the hard part, basically everybody who have studied a bit of physics understands the schrödinger equation and the wave part, the hard part is the particle like behavior which causes the wave to break down. Meaning it isn't a wave, waves doesn't break down like that, waves doesn't just gather together into some coherent state randomly. That is the hard part, if you can't explain that then don't say that QM is easy.
kgwgk 7y ago
Many interactions are perfectly described by Schroedinger's equation. The interactions inside an atom, for example. Or the operation of a quantum computer. What "occurs" (that's the part we don't really understand) with probability defined by wave function is "measurement" but not every interaction is a measurement. A measurement is the macroscopic effect of interactions (which may or may not be fully described by Schroedinger's equation).