The Aharonov-Bohm Effect and the Quantum Interference Phase Shift due to an Electrostatic Field

Abstract

Diffraction and interference effects of charged particles are well-known and accepted wave-particle phenomena in quantum physics. However the phase shift, observable in an interference pattern, introduced between two coherent electron beams propagating around a magnetic field through a field free region (Aharonov and Bohm 1959), has been the subject of an extensive debate both from theoretical and experimental viewpoints. The significance of this experiment, which concerns the physical meaning of fields and potentials in electromagnetism and quantum theory, has been recently emphasized by Olariu and Popescu (1985). The authors compare this significance with that which Michelson’s experiment had in demonstrating the limitations of the traditioiial notions of space and time. This quite surprising interference effect has been verified and confirmed by a number of experiments (for a review see Olariu and Popescu (1985)) the last of which regards the investigation of completely shielded superconducting toruses by means of electron holography (Tonomura et al., 1986). This experiment definitely demonstrates that electrons do not directly experience any magnetic field, therefore the phase difference cannot be attributed to an external leakage field or to Lorentz-force effects on the portion of the electron beam going through the magnet, as some authors have defended.