Asymmetric arms maximise visibility in hot-electron interferometers

TL;DR

This paper theoretically investigates a quantum Hall edge channel Mach-Zehnder interferometer with single-electron sources, revealing that asymmetric arms can maximize interference visibility by counteracting phase averaging effects.

Contribution

It introduces the concept that asymmetric interferometer arms enhance visibility, challenging the traditional symmetric design approach in quantum electron interferometry.

Findings

Maximum visibility occurs with asymmetric arms up to a micron in length.

Energy-dependent delay times influence interference patterns significantly.

Asymmetry can mitigate phase-averaging effects, improving coherence.

Abstract

We consider theoretically an electronic Mach-Zehnder interferometer constructed from quantum Hall edge channels and quantum point contacts, fed with single electrons from a dynamic quantum dot source. By considering the energy dependence of the edge-channel guide centres, we give an account of the phase averaging in this set up that is particularly relevant for the short, high-energy wavepackets injected by this type of electron source. We present both analytic and numerical results for the energy-dependent arrival time distributions of the electrons and also give an analysis of the delay times associated with the quantum point contacts and their effects on the interference patterns. A key finding is that, contrary to expectation, maximum visibility requires the interferometer arms to be different in length, with an offset of up to a micron for typical parameters. By designing interferometers that incorporate this asymmetry in their geometry, phase-averaging effects can be overcome such that visibility is only limited by other incoherent mechanisms.