Conservation of angular momentum on a single-photon level

TL;DR

This paper investigates the conservation of orbital angular momentum in single-photon pumped spontaneous parametric down-conversion, demonstrating the potential for generating high-dimensional entangled photon pairs without waveguides.

Contribution

First experimental study of OAM conservation in SPDC pumped by single photons, enabling new avenues for high-dimensional entanglement generation.

Findings

Confirmed OAM conservation in single-photon pumped SPDC

Demonstrated cascaded down-conversion without waveguides

Paved the way for multi-photon high-dimensional entanglement experiments

Abstract

Identifying conservation laws is central to every subfield of physics, as they illuminate the underlying symmetries and fundamental principles. A prime example can be found in quantum optics: The conservation of orbital angular momentum (OAM) during spontaneous parametric down-conversion (SPDC) enables the generation of a photon pair with entangled OAM. In this article, we report on the first study of OAM conservation in SPDC pumped by single photons. Our results present the first implementation of cascaded down-conversion without waveguides, setting the stage for experiments on the direct generation of multi-photon high-dimensional entanglement using all degrees of freedom of light.