# nLab Born rule

Contents

### Context

#### Measure and probability theory

measure theory

probability theory

# Contents

## Idea

The Born rule is the core statement of coordination in the foundations of quantum physics:

In its version for pure states the Born rule says that

then the probability of observing the given eigenstate in a quantum system which is in state $\psi$ equals

$\frac{ \langle \psi \vert P \vert \psi \rangle }{ \langle \psi \vert \psi \rangle }$