Aharonov–Bohm effect

Summary

The Aharonov–Bohm effect is a quantum effect of electromagnetic potentials on charged particles. It occurs in regions where the magnetic field is zero. The particle picks up a phase equal to its charge times the flux enclosed by its path, divided by $\hbar$. This phase shifts an interference pattern. It shows that in quantum mechanics the magnetic vector potential carries physical information that the field alone does not. In geometric terms the phase is the holonomy of a flat connection on a region that is not simply connected. It was predicted by Aharonov and Bohm in 1959, and earlier by Ehrenberg and Siday in 1949.