Weak Measurements in Neutron Optical Experiments

Orateur : Tobias DENKMAYR (Vienna Institute of Atomic and Subatomic Physics)

During the examination of the quantum measurement process Aharonov, Albert and Vaidman introduced the concept of weak measurements, which makes it possible to extract information of a quantum system between the events of pre and postselection. In combination with neutron interferometry, where an interference effect of matter-waves pass-ing through a perfect silicon-crystal interferometer is observed, they are a perfect tool to study the foundations of quantum mechanics. In this talk, two novel neutron optical experiments are presented. While the first one represents the measurement of the spin operator’s weak value, the second one demonstrates the so called “quantum Cheshire Cat” effect : If a quantum system is subject to a certain pre- and postselection, it can behave as if it is spatially separated from one of its properties. In our experiment, the neutron plays the role of the cat and the cat’s grin is represented by the neutron’s spin component along the z direction. The results suggest that the system behaves as if the neutrons go through one beam path, while their magnetic moment travels along the other inside the interferometer.

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