  We study the quantum-mechanical problem of scattering caused by a localized
obstacle that breaks spatial and temporal reversibility. Accordingly, we follow
Maxwell's prescription to achieve a violation of the second law of
thermodynamics by means of a momentum-dependent interaction in the Hamiltonian,
resulting in what is known as Maxwell's demon. We obtain the energy-dependent
Green's function analytically, as well as its meromorphic structure. The poles
lead directly to the solution of the evolution problem, in the spirit of M.
Moshinsky's work in the 1950s. Symmetric initial conditions are evolved in this
way, showing important differences between classical and wave-like
irreversibility in terms of collapses and revivals of wave packets. Our setting
can be generalized to other wave operators, e.g. electromagnetic cavities in a
classical regime.
