Coherence Experiments with Neutron Matter Waves.

Robert Golub, S. K. Lamoreaux

Muhammad Arif

M. Arif, Helmut Kaiser, R. Clothier +4 more

We report the results of a neutron interferometry experiment where for the first time (to our knowledge) a phase shift of a neutron de Broglie wave induced by moving matter has been successfully measured. This experiment is the quantum-mechanical analog of the optical Fizeau effect. The observed phase shift is caused by the motion of matter itself, and not by the motion of its boundaries. The experimental results are found to be in good agreement with the theoretical predictions. Some unexpected and previously unreported neutron wave interference effects observed during the experiment are also reported.

Pierre Meystre

J. Felber, R. Gähler, C. Rausch +1 more

We investigate the time-dependent Schr\"odinger equation for the case of a plane matter wave incident on an oscillating potential step. Approximate solutions are given for different regimes of the problem. The resulting energy spectra are quantized. This may either be interpreted as a phase modulation of the wave or as a coherent multiphonon exchange. A comparison to the results that apply for a beam of classical particles is made. In particular, the transition from the quantum-mechanical to the classical case is examined. We have performed an experiment with very cold neutrons that clearly revealed the discussed effects. Energy splittings of 2.8 to 9.1 neV of the reflected waves were analyzed with an energy resolution of \ensuremath{\sim}1 neV, thus demonstrating the feasibility of such high-resolution experiments with neutron reflectometry. \textcopyright{} 1996 The American Physical Society.

Helmut Rauch

Neutron matter-wave optics provides the basis for new quantum experiments and a step towards applications of quantum phenomena. Most experiments have been performed with a perfect crystal neutron interferometer where widely separated coherent beams can be manipulated individually. Various geometric phases have been measured and their robustness against fluctuation effects has been proven, which may become a useful property for advanced quantum communication. Quantum contextuality for single particle systems shows that quantum correlations are to some extent more demanding than classical ones. In this case entanglement between external and internal degrees of freedom offers new insights into basic laws of quantum physics. Non-contextuality hidden variable theories can be rejected by arguments based on the Kochen-Specker theorem.