Probing the Goos-Hanchen effect with entangled neutrons

The fact that rays incident upon and reflected from a surface cross at a point slightly behind the reflecting surface was first postulated by Sir Isaac Newton and measured in 1947 for light by Goos and Hanchen (GH). A 2010 experiment on Offspec showed a phase shift between oppositely polarized neutrons reflected from a magnetic surface that was interpreted as evidence for a neutron GH effect. Theories purporting to describe the GH effect for neutrons give different results. We propose accurate measurements on Larmor to resolve this issue. The experiments will be guided by on-going dynamical simulations of entangled neutrons reflecting from surfaces and bear on the potential of using entangled neutrons as a new probe of matter.