Completely mixing quantum open systems and quantum fractals

Departing from classical concepts of ergodic theory, formulated in terms of probability densities, measures describing the mixing behavior and the los s of information in quantum open systems are proposed. As application we di scuss the chaotic outcomes of continuous measurement processes in the EEQT framework. Simultaneous measurement of four noncommuting spin components is shown to lead to a chaotic jumps on the quantum spin sphere and to generat e specific fractal images of a nonlinear iterated function system. (C) 2001 Published by Elsevier Science B.V.