The most robust entangled state of light
  We study how photon absorption losses degrade the bipartite entanglement of entangled states of light. We consider two questions: (i) what state contains the smallest average number of photons given a fixed amount of entanglement? and (ii) what state is the most robust against photon absorption? We explain why the two-mode squeezed state is the answer to the first question but not quite to the second question. 
S.J. van Enk and O. Hirota