Coherence and visibility in Fano interferometers

TL;DR

This paper investigates the unique interference properties of Fano interferometers, revealing that traditional coherence-visibility relations do not apply and proposing a new method to quantify coherence using spectral asymmetry.

Contribution

It demonstrates that the conventional interference visibility-coherence relation is invalid for Fano interferometers and introduces a novel approach to measure coherence through spectral asymmetry.

Findings

Traditional visibility-coherence relation does not hold for Fano interferometers.

Spectral asymmetry can be used to quantify coherence.

Fano spectra asymmetry provides a new coherence measurement method.

Abstract

Interferometry is an indispensable tool across all the natural sciences. Recently, a new type of interferometer based on phase-sensitive Fano resonances has been proposed and implemented. In these Fano interferometers, the two arms are formed by a spectrally broad continuum channel, and a spectrally narrow resonant bound state scattering channel, respectively. We show that the textbook relation between interference visibility and coherence known from double-slit- or Mach-Zehnder-interferometers does not apply to Fano interferometers, because the physical origin of the interference extrema is different. We then show how instead the asymmetry of Fano spectra can be exploited to quantify coherence in Fano interferometers.