  Both the quantum mechanical and classical Bells experiment are within the
focus of this paper. The fact that one measures different probabilities in both
experiments is traced back to the superposition of two orthogonal but
nonentangled substates in the quantum mechanical case. This superposition
results in an interference term that can be splitted into two additional states
representing a sink and a source of probabilities in the classical event space
related to Bells experiment. As a consequence, a statistical operator can be
related to the quantum mechanical Bells experiment that contains already
negative quasi probabilities, as usually known from quantum optics in
conjunction with the Glauber-Sudarshan equation. It is proven that the
existence of such negative quasi probabilities are neither a sufficient nor a
necessary condition for entanglement. The equivalence of using an interaction
picture in a fixed basis or of employing a change of basis to describe Bells
experiment is demonstrated afterwards. The discussion at the end of this paper
regarding the application of the complementarity principle to the quantum
mechanical Bells experiment is supported by very recent double slit experiments
performed with polarization entangled photons.
