Isothermal Maxwell Daemon: Swing (fish-trap) model of particle pumping

A new model of a small open quantum system (swing or fish-trap model) is presented and solved. Analysis of the Hamiltonian as well as quantum solution shows that the model yields pumping of particles (ions, electrons) from one to another side preserving or even slightly increasing (on account of energy of the infinite thermodynamic bath) the mean particle energy. The effect reminds of the Maxwell daemon (working here, however, in isothermal conditions) and is due to a combination of a fast relaxation of the scatterer (central system) in intermediate states owing to its coupling to the thermodynamic bath with a special type of its instability in the intermediate state.