Quantum coherence engineering in the integer quantum Hall regime

TL;DR

This paper demonstrates how tuning the coupling between edge states in the integer quantum Hall regime can significantly enhance quantum coherence, with implications for quantum interference control and quantum Hall system performance.

Contribution

It introduces a method to control quantum coherence via a decoupling gate, revealing the impact of inter-edge state coupling on quantum interference and coherence length.

Findings

Coherence length can be doubled by tuning temperature dependence.

Decoupling reduces coupling between edge states, enhancing phase coherence.

Inter-edge coupling influences the bias dependence of quantum interference.

Abstract

We present an experiment where the quantum coherence in the edge states of the integer quantum Hall regime is tuned with a decoupling gate. The coherence length is determined by measuring the visibility of quantum interferences in a Mach-Zehnder interferometer as a function of temperature, in the quantum Hall regime at filling factor two. The temperature dependence of the coherence length can be varied by a factor of two. The strengthening of the phase coherence at finite temperature is shown to arise from a reduction of the coupling between co-propagating edge states. This opens the way for a strong improvement of the phase coherence of Quantum Hall systems. The decoupling gate also allows us to investigate how inter-edge state coupling influence the quantum interferences' dependence on the injection bias. We find that the finite bias visibility can be decomposed into two contributions: a Gaussian envelop which is surprisingly insensitive to the coupling, and a beating component which, on the contrary, is strongly affected by the coupling.