Neutron interferometry for precise characterization of quantum systems*

Neutron interferometry (NI) is among the most precise techniques used to test the postulates of quantum mechanics. It has demonstrated coherent spinor rotation and superposition, gravitationally induced quantum interference, the Aharonov-Casher effect, violation of a Bell-like inequality, and generation of a single-neutron entangled state. As massive, penetrating and neutral particles neutrons now provide unique capabilities in classical imaging applications that we seek to extend to the quantum domain. We present recent results on NI measurements of quantum discord in a bipartite quantum system\footnote{``Quantum correlations in a noisy neutron interferometer,'' C. J. Wood {\em et al., Phys. Rev. A} {\bf 90}, 032315 (2014)} and neutron orbital angular momentum multiplexing,\footnote{``Controlling neutron orbital angular momentum,'' C. W. Clark {\em et al., Nature} {\bf 525}, 504 (2015)} and review progress on our commissioning of a decoherence-free-subspace NI user facility at the NIST Center for Neutron Research.\footnote{``Experimental realization of decoherence-free subspace in neutron interferometry,'' D. A. Pushin {\em et al., Phys. Rev. Lett.} {\bf 107}, 150401 (2011)}