Probing the BCS-BEC crossover with photons in a nonlinear optical fiber
  We propose a scheme where strongly correlated photons generated inside a hollow-core one-dimensional fiber filled with two cold atomic species can be used to simulate the BCS-BEC crossover. We first show how stationary light-matter excitations (polaritons) in the system can realize an optically tunable two component Bose-Hubbard model, and then analyze the optical parameters regime necessary to generate an effective Fermi-Hubbard model of photons exhibiting Cooper pairing. The characteristic correlated phases of the system can be efficiently observed due to the {\it in situ} accessibility of the photon correlations with standard optical technology. 
Mingxia Huo, Changsuk Noh, B. M. Rodr\'iguez-Lara and Dimitris G.   Angelakis
quant-ph cond-mat.quant-gas cond-mat.str-el cond-mat.supr-con