Asymmetric arms maximize visibility in hot-electron interferometers

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 centers, we give an account of the phase averaging in this setup that is particularly relevant for the short, high-energy wave packets 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.This research was supported by EPSRC Grant No. EP/P034012/1. S.R. was supported by the María de Maeztu Program for units of Excellence in R&D (Grant No. MDM-2017-0711). L.A.C. also acknowledges support from the Foundation for Polish Science within the “Quantum Optical Technologies” project carried out within the International Research Agendas programme cofinanced by the European Union under the European Regional Development Fund. H.S.S. was supported by the Korea NRF (SRC Center for Quantum Coherence in Condensed Matter, Grant No. 2016R1A5A1008184). M.K. was supported by the UK Department for Business, Energy, and Industrial Strategy, and by the European Metrology Programme for Innovation and Research (EMPIR). This project 17FUN04 SEQUOIA has received funding from the EMPIR programme cofinanced by the Participating States and from the European Union's Horizon 2020 research and innovation programme