  We propose a scheme to realize the two-axis counter-twisting spin-squeezing
Hamiltonian inside an optical cavity with the aid of phase-locked atom-photon
coupling. By careful analysis and extensive simulation, we demonstrate that our
scheme is robust against dissipation caused by cavity loss and atomic
spontaneous emission, and it can achieve significantly higher squeezing than
one axis twisting. We further show how our idea can be extended to generate
two-mode spin-squeezed states in two coupled cavities. Due to its easy
implementation and high tunability, our scheme is experimentally realizable
with current technologies.
