Strong and weak single particle nonlocality induced by time-dependent boundary conditions

We investigate the issue of single particle nonlocality in a quantum system subjected to time-dependent boundary conditions. We first prove that contrary to earlier claims, there is no strong nonlocality: a quantum state localized at the center of a well with infinitely high moving walls is not modified by the wall’s motion. We then show the existence of a weak form of nonlocality: when a quantum state is extended over the well, the wall’s motion induces a current density all over the box instantaneously. We indicate how this current density can in principle be measured by performing weak measurements of the particle’s momentum.