Observation of a magnetic shift in neutron whispering-gallery states

We developed experimental and theoretical methods to create and describe high-resolution whispering-gallery interference patterns and show the feasibility of measuring their small shifts by external interactions. Such experiments can be used to search for extra fundamental interactions, time parity violations, nonzero electric charges, precisely measuring the gravitational properties of (anti)matter, parity violations, neutron polarizability, quantum reflection, surface state effects, etc. Here, we measure a magnetic shift of such a neutron pattern $\delta g\mathrm{/}g\sim (6.5\pm {0.8}_{st}\pm {1.2}_{sys})\cdot {10}^{-4}$, and our sensitivity to spin-dependent differences between the scattering lengths was $\delta b_n\mathrm{/}{b}_n\sim {10}^{-4}$.