Cascaded entanglement enhancement
Zhihui Yan, Xiaojun Jia, Xiaolong Su, Zhiyuan Duan, Changde Xie, Kunchi Peng · Physical Review A · 2012
We present a cascaded system consisting of three nondegenerate optical parametric amplifiers (NOPAs) for the generation and the enhancement of quantum entanglement of continuous variables. The entanglement of optical fields produced by the first NOPA is successively enhanced by the second and the third NOPAs from $\ensuremath{-}5.3$ to $\ensuremath{-}8.1$ dB below the quantum noise limit. The dependence of the enhanced entanglement on the physical parameters of the NOPAs and the reachable entanglement limitation for a given cascaded NOPA system are calculated. The calculation results are in good agreement with the experimental measurements.