Theory of Electron Interference Experiments

J. Arol Simpson

Paweł Machnikowski

A single-electron two-path interference (Young) experiment is considered theoretically. The decoherence of an electron wave packet due to the which path trace left in a conducting (metallic) plate placed under the electron trajectories is calculated using the many-body quantum description of the electron gas reservoir.

C. S. Chang, P. Stehle

The quantum theory of interference effects is given. Three experiments of particular interest are treated: (i) Young-type experiments, (ii) production of beats in photocurrents, and (iii) optical modulation of electron beams. These have been of considerable interest in recent experiments using lasers. We show that they can be accounted for by the same simple quantum-mechanical principle. In the first case, we include the effect of interference in single-photon processes and correlations in multiphoton processes. Here the method of Weisskopf and Wigner is used, and useful distinction between the concept of interference and correlation is proposed. We further emphasize the dynamical aspect of the theory. In the last two cases, we use the standard method of quantum electrodynamics. Here we view the actual experimental setup as being described by a single dynamical process. The description involves the use of nonstationary states as the relevant states to describe the successive excitation. It is shown that all the three phenomena analyzed are closely related.

Pier Giorgio Merli, G.F. Missiroli, G. Pozzi

R.C. Liu, Brian Odom, Y. Yamamoto +1 more

Mark P. Silverman

Interference experiments characterized by the degree of first-order coherence (Young’s fringes, Fresnel, and Fraunhofer diffraction, etc.) have been performed with massive particles, in particular electrons and neutrons, as well as with light. Optical intensity interference or correlation experiments characterized by the degree of second-order coherence have not yet been performed with particles. The theory for such experiments shows striking differences in the behavior of electrons compared with that of light deriving from the differences in quantum statistics and charge. Photons are neutral bosons. They can be prepared in states that exhibit bunching, no bunching, or antibunching; they are unaffected by the presence of electromagnetic potentials. Electrons are charged fermions. Theory indicates that they exhibit antibunching regardless of the coherence of the source, and that their degree of second-order coherence can be influenced by electromagnetic fields through which they do not pass. A remarkable example is the Hanbury Brown-Twiss experiment with electrons that have interacted locally with the vector potential of an inaccessible magnetic field. The electron intensity correlation at two detectors is shown to be sensitive to the confined magnetic flux; experimental conditions differ considerably from those of the well-known Aharonov-Bohm effect.