A nonlinear stochastic process is presented that, for each realization and for large times, reproduces Lüder's projection postulate. The corresponding density operator undergoes a linear evolution reproducing von Neumann's projection postulate. The violation of the Bell inequality, for instance, is described with the two apparatus acting independently on the composed system.

• Received 19 December 1983

DOI:https://doi.org/10.1103/PhysRevLett.52.1657