Quantum precession of cold neutron spin using multilayer spin splitters and a phase-spin-echo interferometer

Abstract

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