Neutron spin echo is a "quantum tale of two paths''

We describe an experiment that strongly supports a two-path interferometric model in which the spin-up and spin-down components of each neutron propagate coherently along spatially separated parallel paths in a typical neutron spin echo small angle scattering (SESANS) experiment. Specifically, we show that the usual semi-classical, single-path treatment of the Larmor precession of a polarized neutron in an external magnetic field predicts a damping as a function of the spin-echo length of the SESANS signal obtained with a periodic phase grating when the transverse width of the neutron wave packet is finite. However, no such damping is observed experimentally, implying either that the Larmor model is incorrect or that the transverse extent of the wave packet is very large. In contrast, we demonstrate theoretically that a quantum-mechanical interferometric model in which the two mode-entangled (i.e. intraparticle entangled) spin states of a single neutron are separated in space when they interact with the grating accurately predicts the measured SESANS signal, which is independent of the wave packet width

Applying Resonant Spin Flippers with Poleshoes and Longitudinal Radio Frequency Fields to Time of Flight MIEZE

A time of flight MIEZE spectrometerstudyis presented. The instrumentuses solenoid radio frequency(RF)spin flipperswithsquare pole shoes and a magnetic yoke. These flippers can achieve higherstaticfields than conventional resonant RF spin flippers, which employ an air core.High fields are crucial for the construction of a high resolution and compact MIEZE spectrometer.Using both types of flipperstwo MIEZE spectrometer configurationsare constructed and comparedon the same beam line. It was demonstratedthat the pole shoe/solenoid coil RF flipperscan achieve a MIEZE signal, which is similarin quality to theconventionalreferencesetup.The highest obtained modulation frequency was 100kHz.Instrumenten groepRST/Neutron and Positron Methods in MaterialsTechnici Poo