A new non-local effect in quantum mechanics

The Aharonov-Bohm effect affords a beautiful insight into the non-local nature of quantum theory. Unfortunately, because of the topological aspects to that effect, which are quite fascinating in their own right, there is an unfortunate tendency to connect these two independent elements. The present effect exhibits the non-locality, free of topological considerations, although it is related to the Berry phase, another much-discussed recent phenomenon. The effect consists of keeping a particle confined to a small region of a box with infinite walls. If the wall of the box is moved, then even though the particle is nowhere near the wall, it will experience a phase shift, which in principle is subject to experimental verification. (orig.)