Chaos, Fractal and Quantum Poincare Recurrences in Diamagnetic Kepler   Problem
  The statistics of quantum Poincare recurrences in Hilbert space for diamagnetic hydrogen atom in strong magnetic field has been investigated. It has been shown that quantities characterizing classical chaos are in a good agreement with the ones that are used to describe quantum chaos. The equality of classical and quantum Poincare recurrences has been shown. It has been proved that one of the signs of the emergence of quantum chaos is the irreversible transition from a pure quantum mechanical state to the mixed one. 
A.Ugulava, L.Chotorlishvili, T.Kereselidze, V.Skrinnikov