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St. Sponar, G. Sulyok, J. Erhart, J. Klepp, C. Schmitzer, H. Geppert, K. Durstberger-Rennhofer, G. Badurek, M. Ozawa, Y. Hasegawa:
"Foundations of Quantum Mechanics explored with Neutrons";
Talk: Quantum Africa 2, Mont aux Sources Hotel, Northern Drakensberg, Südafrika; 2012-09-03 - 2012-09-07.

Neutron interferometry, where an interference effects of matter waves passing through a perfect silicon-crystal interferometer is observed, and neutron polarimetry, also referred to as spin-interferometry, have established as a powerful tool for investigation of fundamental quantum mechanical concepts with massive particles. Utilizing neutron interferometry tests of non-contextual realistic theories, by means of Bell inequalities or the Kochen-specker theorem, have been performed successfully. Furthermore, we investigated the influence of geometric phases on Bell measurements, and achieved preparation of a Greenberger-Horne-Zeilinger entanglement consisting different degree of freedom, in a single neutron system. Tests of contextual realistic models require a significantly higher contrast and are therefore not feasible with neutron interferometry. Falsification of a contextual realistic model, analogous to Leggett´s non-local realistic model for entangled pairs of particles, has been accomplished using neutron polarimetry. Our experimental data rule out classes of contextual, as well as non-contextual realistic theories and are fully in favor of quantum mechanics. In a more recent experiment a fundamental principle of quantum mechanics, i.e., Heisenberg´s uncertainty principle is studied, demonstrating validity of a new universally valid error-disturbance uncertainty relation. In the neutron optical experiment the error of a spin-component measurement and the disturbance caused on another spin-measurement are recorded, clearly confirming that both error and disturbance obey this universally valid uncertainty relation but violate the original one in a wide range of experimental parameters.

quantum, neutron, spin, polarimeter, uncertainty relation