Using a quantum theory for an ensemble of three-level atoms (lambda) placed in an optical cavity abd driven by electromagnetic fields, we show that the long-lived spin associated with the ground state sublevels can be squeezed. Two kinds of squeezing are obtained: self-spin squeezing, when the input fields are coherent states and the atomic ensemble exhibit a large non-linearity; squeezing transfer, when one of the incoming fields is squeezed.
@article{arxiv.quant-ph/0209023,
title = {Atomic squeezing in a Lambda system},
author = {A. Dantan and M. Pinard and V. Josse and N. Nayak and P. R. Berman},
journal= {arXiv preprint arXiv:quant-ph/0209023},
year = {2009}
}