Observation of pair tunneling and coherent destruction of tunneling in   arrays of optical waveguides
  We report on the experimental realization of a photonic system that simulates the one-dimensional two-particle Hubbard model. This analogy is realized by means of two-dimensional arrays of coupled optical waveguides, fabricated using femtosecond laser inscription. By tuning the analogous "interaction strength", we reach the strongly-interacting regime of the Hubbard Hamiltonian, and demonstrate the suppression of standard tunneling for individual "particles". In this regime, the formation of bound states is identified through the direct observation of pair tunneling. We then demonstrate the coherent destruction of tunneling (CDT) for the paired particles in the presence of an engineered oscillating force of high frequency. The precise control over the analogous "interaction strength" and driving force offered by our experimental system opens an exciting route towards quantum simulation of few-body physics in photonics. 
Sebabrata Mukherjee, Manuel Valiente, Nathan Goldman, Alexander   Spracklen, Erika Andersson, Patrik \"Ohberg, and Robert R....
physics.optics cond-mat.mes-hall quant-ph