Quantum Variance and Ergodicity for the baker's map
  We prove a Egorov theorem, or quantum-classical correspondence, for the quantised baker's map, valid up to the Ehrenfest time. This yields a logarithmic upper bound for the decay of the quantum variance, and, as a corollary, a quantum ergodic theorem for this map. 
Mirko Degli Esposti (BOLOGNA), St\'ephane Nonnenmacher (SPhT), Brian   Winn (BOLOGNA)