Classical Bound for Mach-Zehnder Super-Resolution

TL;DR

This paper establishes a classical limit for super-resolving oscillations in Mach-Zehnder interferometers, providing a fundamental test to distinguish quantum effects from classical phenomena in multiphoton measurements.

Contribution

It derives a classical bound for Mach-Zehnder super-resolution, clarifying the quantum nature of observed super-resolving oscillations and offering a practical test for non-classicality.

Findings

Classical bound for super-resolution visibility established

Experimental data shows quantum super-resolution exceeds classical limits

Super-resolution identified as a distinctive quantum effect

Abstract

The employment of path entangled multiphoton states enables measurement of phase with enhanced precision. It is common practice to demonstrate the unique properties of such quantum states by measuring super-resolving oscillations in the coincidence rate of a Mach-Zehnder interferometer. Similar oscillations, however, have also been demonstrated in various configurations using classical light only; making it unclear what, if any, are the classical limits of this phenomenon. Here we derive a classical bound for the visibility of super-resolving oscillations in a Mach-Zehnder. This provides an easy to apply, fundamental test of non-classicality. We apply this test to experimental multiphoton coincidence measurements obtained using photon number resolving detectors. Mach-Zehnder super-resolution is found to be a highly distinctive quantum effect.