A quantum delayed choice experiment

TL;DR

This paper reports a quantum delayed choice experiment using a quantum controlled beam-splitter, demonstrating that photons exhibit genuinely quantum behavior with strong Bell inequality violations, challenging classical particle-wave models.

Contribution

The experiment introduces a quantum-controlled approach to the delayed choice experiment, allowing simultaneous investigation of wave and particle behaviors and testing quantum nature via Bell inequalities.

Findings

Strong Bell inequality violations observed.

Photons exhibit behavior incompatible with classical models.

Quantum control enables simultaneous wave-particle analysis.

Abstract

Quantum systems exhibit particle-like or wave-like behaviour depending on the experimental apparatus they are confronted by. This wave-particle duality is at the heart of quantum mechanics, and is fully captured in Wheeler's famous delayed choice gedanken experiment. In this variant of the double slit experiment, the observer chooses to test either the particle or wave nature of a photon after it has passed through the slits. Here we report on a quantum delayed choice experiment, based on a quantum controlled beam-splitter, in which both particle and wave behaviours can be investigated simultaneously. The genuinely quantum nature of the photon's behaviour is tested via a Bell inequality, which here replaces the delayed choice of the observer. We observe strong Bell inequality violations, thus showing that no model in which the photon knows in advance what type of experiment it will be confronted by, hence behaving either as a particle or as wave, can account for the experimental data.