A double-loop perfect crystal neutron interferometer has been used for novel quantum state reconstruction experiments. For the measurement of combined spatial and momentum distributions a quadrature method has been used which permits the reconstruction of the related Wigner function. When neutrons pass through narrow slits the transverse momentum quantization causes a confinement-induced phase shift which has been measured by neutron inter-ferometry. The related wave fields for reflecting and absorbing walls have been calculated and mapped in form of wave carpets. It is of interest to note that just those neutrons contribute to the phase shift which classically do not touch the walls. In another set-up installed at the pulsed neutron spallation source ISIS neutrons can be trapped between perfect crystal plates for several seconds. This enables a multiple passage of the same neutron through a spin rotation unit, which provides the basis for new Zeno-effect experiments. Unavoidable quantum losses will be discussed and it will be shown how they become relevant for the quantum measuring process.