QUANTUM PRECESSION OF COLD NEUTRON SPIN USING MULTILAYER SPIN SPLITTERS AND A PHASE-SPIN-ECHO INTERFEROMETER

We demonstrate a method of inducing neutron spin rotation in a field-f ree region of space. A multilayer mirror (''spin splitter'') is used a s an optically active element, providing a longer path length for one spin eigenstate of a polarized neutron than for the other. This produc es a relative phase shift between the two eigenstates, which is interp reted, quantum mechanically, as precession of the neutron spin. We sho w that the spin precession of our technique is equivalent to Larmor pr ecession in a magnetic field, though our method has no such classical analog and occurs on shorter (e.g., 20 nm) length scales. We also demo nstrate a ''phase spin-echo'' interferometer based on a pair of multil ayer spin splitters.