A quantum mechanical version of the paper by E. Schrödinger “Über die Umkehrung der Naturgesetze”

The principal results of Schrödinger's paper are reviewed and a possible extension of his formalism for diffusion processes to general quantum mechanical processes is given. The formalism is not in accord with the general theory of transformation of quantum mechanics and violates the basic assumption of the unpredictable change of a system due to a measurement. Nevertheless, the formalism leads to a density operator which is constructed according to accepted quantum mechanical rules.In memory of Erwin Schrödinger, 1887–1961.