The postulates of quantum mechanics, written in the braket notation, are as follows:
where a⟩ is the eigenvector with eigenvalue a. After the measurement is conducted, the state is a⟩.
In this framework, Heisenberg's uncertainty principle becomes a theorem about noncommuting operators. Furthermore, both continuous and discrete observables may be accommodated; in the former case, the Hilbert space is a space of squareintegrable wavefunctions.
In the Everett manyworlds interpretation of quantum mechanics, postulate (3) is demoted to a phenomenological principle; see quantum decoherence.
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