Spin-Squeezing and Light Entanglement in Coherent Population Trapping
  We show that high squeezing and entanglement can be generated at the output of a cavity containing atoms interacting with two fields in a Coherent Population Trapping situation, on account of a non-linear Faraday effect experienced by the fields close to a dark-state resonance in a cavity. Moreover, the cavity provides a feedback mechanism allowing to reduce the quantum fluctuations of the ground state spin, resulting in strong steady state spin-squeezing. 
Aurelien Dantan (LCFIO), Jean Cviklinski (LKB - Jussieu), Elisabeth   Giacobino (LKB - Jussieu), Michel Pinard (LKB - Jussieu)