Lower order and higher order entanglement in $87Rb$ $5S-5P-5D$ hyperfine   manifold modeled as a four-wave mixing process
  Possibilities of generation of lower order and higher order intermodal entanglement in 87Rb 5S-5P-5D hyperfine manifold are rigorously investigated using Sen-Mandal perturbative technique by showing the equivalence of the system with the four-wave mixing (FWM) process. The investigation has revealed that for a set of experimentally realizable/relevant parameters we can observe lower order and higher order intermodal entanglement between pump and signal modes, signal and idler modes, and idler and pump modes in a FWM process associated with the 87Rb 5S-5P-5D hyperfine manifold. In addition, trimodal entanglement involving pump, signal and idler modes is also reported. 
Moumita Das, Biswajit Sen, Ayan Ray and Anirban Pathak
quant-ph