We show that the two-axis counter twisting interaction squeezes a coherent spin state into three states of interest in quantum information, namely, the twin-Fock state, the equally-weighted superposition state, and the state that achieves the Heisenberg limit of optimal sensitivity defined by the Cramer-Rao inequality in addition to the well-known Heisenberg-limited state of spin fluctuations.
@article{arxiv.1410.4640,
title = {Precision Measurements Using Squeezed Spin States via Two-axis Counter-twisting Interactions},
author = {Emi Yukawa and Gerard Milburn and Masahito Ueda and Kae Nemoto},
journal= {arXiv preprint arXiv:1410.4640},
year = {2015}
}