Observation of polarized neutron interference in spin space

Abstract

The coherent superposition of particle quantum states resulting from different spatial paths showswell-known interference effects. Another type of interference is Larmor precession, which can bedescribed as neutron wave interference in spin space, i.e. interference on the same spatialpath. Here we show several new manifestations of interference phenomena of the latter type. Theinterference is produced by coherent population of different Iz = ±½ spin states in apolarized neutron beam between two resonant radio-frequency (RF) spin flippers. Their spin flipprobability, and thus the occupation numbers of the spin states, can be tuned between 0 and 1 bychanging the RF amplitude. This leads to interference effects in the polarization since the energyexchanged between the RF field and spin yields different phase evolution in the spatial parts ofthe neutron states. Depending on the preparation of the initial neutron states, five values for thetime-independent phase difference between the final neutron states can be observed.