Spin squeezing inequalities for arbitrary spin
  We determine the complete set of generalized spin squeezing inequalities, given in terms of the collective angular momentum components, for particles with an arbitrary spin. They can be used for the experimental detection of entanglement in an ensemble in which the particles cannot be individually addressed. We also present a large set of criteria involving collective observables different from the angular momentum coordinates. We show that some of the inequalities can be used to detect k-particle entanglement and bound entanglement. 
Giuseppe Vitagliano, Philipp Hyllus, Inigo L. Egusquiza, Geza Toth
quant-ph cond-mat.quant-gas physics.atom-ph