Entangling atoms in bad cavities
  We propose a method to produce entangled spin squeezed states of a large number of atoms inside an optical cavity. By illuminating the atoms with bichromatic light, the coupling to the cavity induces pairwise exchange of excitations which entangles the atoms. Unlike most proposals for entangling atoms by cavity QED, our proposal does not require the strong coupling regime g^2/\kappa\Gamma>> 1, where g is the atom cavity coupling strength, \kappa is the cavity decay rate, and \Gamma is the decay rate of the atoms. In this work the important parameter is Ng^2/\kappa\Gamma, where N is the number of atoms, and our proposal permits the production of entanglement in bad cavities as long as they contain a large number of atoms. 
Anders S. Sorensen and Klaus Molmer