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 Letter, we report on the observation of OAM conservation in SPDC pumped on the single-photon level by a preceding SPDC process. We implement this cascaded down-conversion scheme in free space, without waveguide confinement, and thereby set the stage for experiments on the direct generation of multiphoton high-dimensional entanglement using all degrees of freedom of light.
| Original language | English |
|---|---|
| Article number | 203601 |
| Journal | Physical Review Letters |
| Volume | 134 |
| DOIs | |
| Publication status | Published - 20 May 2025 |
| MoE publication type | A1 Journal article-refereed |
Funding
The authors thank Robert W. Boyd and Boris Braverman for fruitful discussions at an early stage of the experiment. The authors acknowledge the support of the Research Council of Finland through the Photonics Research and Innovation Flagship (PREIN—decision 346511). L. K. acknowledges the support of the Vilho, Yrjö, and Kalle Väisälä Foundation of the Finnish Academy of Science and Letters. R. B. acknowledges the support of the Research Council of Finland through the postdoctoral researcher funding (decision 349120). R. F. acknowledges the support of the Research Council of Finland through the Academy Research Fellowship (decision 332399).