  We present a simplified proof of the von Neumann's Quantum Ergodic Theorem.
This important result was initially published in german by J. von Neumann in
1929.
  We are interested here in the time evolution $\psi_t$, $t\geq 0$, (for large
times) under the Schrodinger equation associated to a given fixed Hamiltonian
$H : \mathcal{H} \to \mathcal{H}$ and a general initial condition $\psi_0$. The
dimension of the Hilbert space $\mathcal{H}$ is finite.
