  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.
