We have established new principles of neutron spin interferometry based on a coherent superposition of (a) two eigen-states of up arrow and down arrow neutron spins or (b) two different energy states with the same up arrow spin state by using non-resonance or resonance neutron spin flippers, respectively. These interferometric states appear as spin precession or time beat, respectively. The phase difference between two spin states can be observed by the neutron spin echo, or by the resonance neutron spin echo. Using these interferometers, we have observed neutron spin precessions through various Fabri-Perot magnetic potentials in the tunneling region. We have also demonstrated that the phase shift of time beat is different depending on whether the magnetic potential is at the upstream of the spin analyzer or at the downstream of it, in the time-beat interferometer. Time-beat neutron interferometry opens new physics on tunneling time and diffraction time problems. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 22]
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