Complementarity, quantum erasure and delayed choice with modified Mach-Zehnder interferometers

TL;DR

This paper presents experiments with modified Mach-Zehnder interferometers demonstrating that interference can be lost or revived without direct interaction, challenging traditional views on measurement and wavefunction collapse in quantum mechanics.

Contribution

The study introduces novel experiments showing interference loss and revival through which-path information manipulation, without direct quantum interaction, questioning standard interpretations.

Findings

Interference can be lost without direct interaction with the quantum.

Erasing which-path information can restore interference fringes.

Wavefunction collapse is not a necessary explanation for the observed phenomena.

Abstract

Often cited dictums in Quantum Mechanics include "observation disturbance causes loss of interference" and "ignorance is interference". In this paper we propose and describe a series of experiments with modified Mach-Zehnder interferometers showing that one has to be careful when applying such dictums. We are able to show that without interacting in any way with the light quantum (or quanta) expected to behave "wave-like", interference fringes can be lost by simply gaining (or having the potential to gain) the which-path knowledge. Erasing this information may revive the interference fringes. Delayed choice can be added, arriving to an experiment in line with Wheeler's original proposal. We also show that ignorance is not always synonym with having the interference fringes. The often-invoked "collapse of the wavefunction" is found to be a non-necessary ingredient to describe our experiments.