Quantum-engineered neutron states and phase space manipulations

In neutron interferometry and in spin-echo systems non-classical neutron quantum states can be produced and manipulated. Schrِdinger cat-like states exhibit two spatially separated regions which are occupied by the neutron at the same time. When used in scattering experiments this enables a direct observation of the local structure and dynamics of matter. A proper description can be obtained by means of Wigner quasi-distribution functions which are common in quantum optics. More complicated quasi-distribution functions have been verified recently by means of a double loop interferometer. These quantum states have the capacity to observe even higher-order correlation functions characterizing condensed matter. The non-local character of quantum theory has also been demonstrated in the behavior of neutrons within narrow slits where typical confinement effects have been observed. Such Casimir-like and Zeno-like phenomena show how neutrons are an attractive tool for quantum optical experiments opening new possibilities of neutron phase space manipulations. A proper treatment of the neutron field can enhance the available neutron intensities considerably. First cooling to ultra-cold neutron energies by cold solid deuterium moderators increases the phase space density, which can be transferred to higher energies by a proper phase space transformer consisting of fast rotating multi-layer mirrors or crystals. Various proposals in this directions will be discussed.