Detection of quantum interference without interference

TL;DR

This paper introduces a new measurement protocol that detects quantum interference without varying experimental parameters, certifies its quantum nature, and distinguishes it from classical interference using cross-correlation measurements.

Contribution

The authors propose a novel protocol that certifies quantum interference without parameter variation and distinguishes it from classical effects, applicable to electronic Mach-Zehnder interferometers.

Findings

Protocol successfully certifies quantum interference without parameter variation

Distinguishes quantum interference from classical interference via null outcomes

Implementation demonstrated with electronic Mach-Zehnder interferometer

Abstract

Quantum interference is typically detected through the dependence of the interference signal on certain parameters (path length, Aharonov-Bohm flux, etc.), which can be varied in a controlled manner. The destruction of interference by a which-path measurement is a paradigmatic manifestation of quantum effects. Here we report on a novel measurement protocol that realizes two objectives: (i) certifying that a measured signal is the result of interference avoiding the need to vary parameters of the underlying interferometer, and (ii) certifying that the interference signal at hand is of quantum nature. In particular, it yields a null outcome in the case of classical interference. Our protocol comprises measurements of cross-correlations between the readings of which-path weakly coupled detectors positioned at the respective interferometer's arms and the current in one of the interferometer's drains. We discuss its implementation with an experimentally available platform: an electronic Mach-Zehnder interferometer (MZI) coupled electrostatically to "detectors" (quantum point contacts).