The influence of the extra classical noises in seed beams on the entanglement between the signal and the idler modes of the output fields generated by a non-degenerate optical parametric amplifier operating at deamplification is investigated theoretically and experimentally.With the increase of the extra classical noises in the seed beams,the correlation degree of the output entangled optical fields,which is scaled by the quantum noise limit,decreases rapidly.The experimental results are in good agreement with the theoretical calculations.
