provides an overview of the state of the art of research in this exciting field. The main emphasis is on the development of a semiclassical formalism that allows one to incorporate the effect of dissipation and decoherence in a precise, yet tractable way into the quantum mechanics of classically chaotic systems. The formalism is employed to reveal how the spectrum of the quantum mechanical propagator of a density matrix is determined by the spectrum of the corresponding classical propagator of phase space density. Simple quantum--classical hybrid formulae for experimentally relevant correlation functions and time-dependent expectation values of observables are derived. The problem of decoherence is treated in detail, and highly unexpected cases of very slow decoherence are revealed, with important consequences for the long-debated realizability of Schrödinger cat states as well as for the construction of quantum computers.weiterlesen