# Observing wave/particle duality of light using topological charge

## TL;DR

This paper demonstrates the wave-particle duality of light using a delayed choice experiment with twisted light, showing that the behavior can be chosen after detection, highlighting quantum complementarity.

## Contribution

It introduces a novel delayed choice experiment with classical laser beams and twisted light, evidencing the ability to select wave or particle behavior post-detection.

## Key findings

- Particle behavior arises from orbital angular momentum quantization.
- Wave or particle behavior can be chosen a posteriori, even after light leaves the interferometer.
- Torque and power measurements confirm the duality with 10% accuracy.

## Abstract

Wave particle duality, also called complementarity, is deeply rooted in the heart of quantum theory. It is fully exemplified in the famous Wheeler's delayed choice experiment where the choice of the wave nature (ability to interfere) or the particle like behavior (path distinguishability) is introduced a posteriori. We perform here a delayed choice experiment in a Mach-Zehnder interferometer, using a classical laser beam and twisted light in a given mode. We entangle the polarization and the twisted internal degrees of freedom, with the which-path-information external degree of freedom of the beam. The particle behavior of light arises from the quantization of the orbital angular momentum. It is demonstrated from torque and light power measurements within 10% accuracy. We then experimentally evidence that the particle or wave behavior of light can be chosen a posteriori, even after the light has left the interferometer, at the moment of the detection.