# Compact sub-kilohertz low-frequency quantum light source based on four-wave mixing in cesium vapor

## TL;DR

This paper presents a compact, diode-laser-pumped quantum light source based on four-wave mixing in cesium vapor, achieving sub-kilohertz intensity-difference squeezing, with potential applications in quantum imaging and metrology.

## Contribution

Demonstrates the first observation of sub-kilohertz intensity-difference squeezing in an atomic system using a compact cesium vapor setup.

## Key findings

- Achieved 6.5 dB of squeezing at 0.7 kHz Fourier frequency
- Confirmed spatial-multi-mode characteristics of the FWM process
- Demonstrated a compact, diode-laser-pumped quantum light source

## Abstract

Using a nondegenerate four-wave mixing (FWM) process based on a double-{\Lambda} scheme in hot cesium vapor, we demonstrate a compact diode-laser-pumped quantum light source for the generation of quantum correlated twin beams with a maximum squeezing of 6.5 dB. The squeezing is observed at a Fourier frequency in the audio band down to 0.7 kHz which, to the best of our knowledge, is the first observation of sub-kilohertz intensity-difference squeezing in an atomic system so far. A phase-matching condition is also investigated in our system, which confirms the spatial-multi-mode characteristics of the FWM process. Our compact low-frequency squeezed light source may find applications in quantum imaging, quantum metrology, and the transfer of optical squeezing onto a matter wave.