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.
@article{arxiv.1803.02882,
title = {Compact sub-kilohertz low-frequency quantum light source based on four-wave mixing in cesium vapor},
author = {Rong Ma and Wei Liu and Zhongzhong Qin and Xiaolong Su and Xiaojun Jia and Junxiang Zhang and Jiangrui Gao},
journal= {arXiv preprint arXiv:1803.02882},
year = {2018}
}