# Quantum beam splitter for orbital angular momentum of light: quantum correlation by four-wave mixing operated in a nonamplifying regime

## TL;DR

This paper demonstrates a quantum beam splitter for light's orbital angular momentum using four-wave mixing in hot cesium vapor, enabling generation of quantum correlated twin beams with OAM in a nonamplifying regime.

## Contribution

It introduces a novel nonamplifying regime of four-wave mixing that acts as a quantum beam splitter for OAM, expanding quantum state engineering capabilities.

## Key findings

- Quantum correlated twin beams with OAM are generated in a nonamplifying regime.
- The FWM process can split a coherent OAM beam into quantum-correlated twin beams.
- The setup can be used as a quantum beam splitter for images.

## Abstract

Nondegenerate four-wave mixing (FWM) process based on a double-$\Lambda$ scheme in hot alkali metal vapor is a versatile tool in quantum state engineering, quantum imaging, and quantum precision measurements. In this Letter, we investigate the generation of quantum correlated twin beams which carry nonzero orbital angular momentums (OAMs) based on the FWM process in hot cesium vapor. The amplified probe beam and the newly generated conjugate beam in the FWM process have the same and opposite topological charge as the seed beam, respectively. We also explore the FWM process operated in a nonamplifying regime where quantum correlated twin beams carrying OAMs can still be generated. In this regime, the FWM process plays the role of quantum beam splitter for the OAM of light, that is, a device that can split a coherent light beam carrying OAM into quantum-correlated twin beams carrying OAMs. More generally, our setup can be used as a quantum beam splitter of images.