Cold neutron spin interferometry and quantum precession of spin

We have successfully developed cold neutron interferometry based on the coherent superposition of the spin eigenstates. These spin interferometry are based on two ideas in principle. One is to split a neutron into two partial waves with their different eigenstates and to superpose them coherently using a new cold neutron spin interferometer. Another is to create versatile phenomena by changing their phase and states using spin dependent optical devices. Quantum mechanically, precession of a polarized neutron spin is described by a relative phase shift between the spin eigenstates. We define the spin precession as 'quantum precession' of neutron spin. We demonstrate a quantum precession of neutron spin by multilayer spin splitters, which originates from an optical phase shift between the spin eigenstates and is magnetic free. Application experiments of the quantum precession and another quantum precession called quantum beat are discussed. (author)