Wigner Function Description of Larmor Interferometry

Recent theoretical developments in neutron interferometry have been focussed on the visualization of Schroedinger-cat like states using the Wigner function formal-ism. An analog description can be attained in Larmor interferometry using wave packets. In this paper the neutron spin-echo effect is presented firstly. It is characterized by Larmor precession of the neutron polarization vector in a constant magnetic field. The rotation of the particles can be reversed in a second magnetic field which points into the opposite direction (spin-echo). Secondly we describe the zero-field spin-echo effect making use of the Wigner formalism too. Here a dynamic spin flipper is flipping the polarized particles inelastically and it is shown that the spectra of the neutrons become time-dependent in a subsequent field-free region.