On position, momentum and their correlation

Position and momentum observables are considered and their correlation is studied for the simplest quantum system of a free particle moving in one dimension. The algebra and the eigenvalue problem for the correlation observable is presented and its possible relevance for the solution of the Pauli problem is analysed. The correlation provides a simple explanation of the shrinking and spreading of wave packets in an interpretation of quantum mechanics based in an ontology suggested by quantum field theory. Several properties and speculations concerning position-momentum correlations are mentioned.