An electron Mach-Zehnder interferometer

Electron interferometry has been applied to many tasks, such as testing the Aharonov-Bohm Effect, viewing domain walls in type II superconductors, and observing atomic steps in thin films. The breakthrough technology of field emission tips combined with electron bi-prisms lead to the realization of such experiments. Proposed, but not realized experiments for electrons include demonstrating the dispersionless nature of the Aharonov-Bohm effect, measuring electron forward scattering amplitude, sensing electric and magnetic field sensing at surfaces [Find References], and investigating electron wall decoherence. Interferometers with low energy and separate beam characteristics seem to be well suited for these proposed experiments.

The dispersionless nature of the Aharanov-Bohm effect can be shown by pushing the Aharonov-Bohm phase shift beyond the longitudinal coherence length. This could be done with a larger solenoid inserted between separated beams at lower electron energies. The cross-section for forward scattering amplitude is appreciable in the below 1kV range and to introduce a gas in one interferometer arm a septum has to be inserted between the separate beams. Field sensing due to an electron interacting with surfaces benefits from increasing the interaction times at low energies. Decoherence experiments also need a low energy electron interferometer.

In atom interferometry a bi-prism interferometer has been developed but most experiments are carried out using grating interferometer. It is debatable if this implies that the grating interferometers are to be preferred. Up until now in electron interferometry only bi-prism interferometers were available. If atom interferometry is any indication then there is great promise for a grating interferometer for electrons. It would be exciting to develop electron grating interferometers and investigate its use for the proposed experiments.

We are working towards this inteferometer.