400.md

December 21, 2023 · View on GitHub

Then the results are that afterward:

For every value of λ\lambda, there is a probability of ∣⟨Ψ∣Ψλ⟩∣2|\langle\Psi|\Psi_\lambda\rangle|^2 that the system is in state ∣Ψλ⟩|\Psi_\lambda\rangle

This is captured by the density matrix formalism as the transition

∣Ψ⟩⟨Ψ∣⇒∑λ∣⟨Ψ∣Ψλ⟩∣2∣Ψλ⟩⟨Ψλ∣|\Psi\rangle\langle\Psi|\Rightarrow\sum_\lambda|\langle\Psi|\Psi_\lambda\rangle|^2|\Psi_\lambda\rangle\langle\Psi_\lambda|

atyy I guess thinking about it classically, Demystifier's argument must be right.