SUPERPOSITION EXPERIMENTS IN NEUTRON INTERFEROMETRY

Coherent superposition of states is responsible for any interference p henomena. Recent neutron interferometry experiments based on postselec tion methods renewed the discussion about quantum non-locality and the quantum measuring process. It has been shown that interference phenom ena can be revived even when the overall contrast of an interference e xperiment vanishes. This indicates a persisting coupling in phase spac e even in cases of spatially separated Schradinger-cat-like situations . More complete quantum experiments also show that a complete retrieva l of quantum states behind an interaction area becomes impossible in p rinciple, which indicates that the irreversible quantum measuring proc ess starts with the first interaction of the quantum system already.