  We propose a broadly applicable formalism for the description of coarse
grained entropy production in quantum mechanical processes. Our formalism is
based on the Husimi transform of the quantum state, which encodes the notion
that information about any quantum state is limited by the experimental
resolution. We show in two analytically tractable cases (the decay of an
unstable vacuum state and reheating after cosmic inflation) that the growth
rate of the Wehrl entropy associated with the Husimi function approaches the
classical Kolmogorov-Sinai entropy. We also discuss various possible
applications of our formalism, including the production of entropy in the early
stages of a relativistic heavy ion collision.
