Feedback-optimized Extraordinary Optical Transmission of   Continuous-variable Entangled States
  We report on the feedback-optimized extraordinary optical transmission of continuous-variable entangled states through a hexagonal metal-hole array. The continuous-variable entanglements from a nondegenerate optical parametric amplifier are first demonstrated to survive after a photon-plasmon-photon conversion process. By controlling the reflected light from the metal-hole array, a significant enhancement of quantum correlations has then been experimentally achieved comparing to the case of without such coherent feedback control. This result presents a useful technique to efficiently recover the substantial reflective losses in the plasmonic circuits for quantum information processing. 
Dong Wang, Chuanqing Xia, Qianjin Wang, Yang Wu, Fang Liu, Yong Zhang,   and Min Xiao
quant-ph physics.optics