Multi-color continuous-variable entangled optical beams generated by NOPOs
Multi-color continuous-variable entangled optical beams generated by NOPOs
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DOI：
10.1007/s11128-013-0594-9
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发表时间：
2013-06
影响因子：
2.5
通讯作者：
A. Tan
中科院分区：
文献类型：
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作者：
A. Tan
我们提出了另一种可扩展的方法来有效地利用非简并光学参量振荡器(NOPO)在阈值以上工作时信号、空转和泵浦三场之间存在的三方纠缠来产生多色纠缠光束。对两级联NOPOO的特殊情况进行了研究，结果表明，五束频率差别很大的光束是由NOPOA(保留信号和闲置光束之一，反射泵浦光束)和NOPOB(输出信号和闲置光束，反射泵浦光束)产生的。通过应用多体连续变量纠缠不可分离的部分转置判据的正性，从理论上证明了这些光束是相互纠缠的。根据实验上可达的系统参数，数值计算了得到的光学纠缠态的部分换位协方差矩阵的辛本征值。给出了实现高五色纠缠的最佳工作条件。由于两个NOPO的腔参数和非线性晶体可以自由选择，因此纠缠态中的子模的频率是可调的，以匹配原子的跃迁频率或低损耗的光纤通信窗口。计算结果为今后利用NOPO在阈值以上高效产生多色纠缠光束的实验提供了直接参考。
We propose an alternative scalable way to generate multi-color entangled optical beams efficiently utilizing the tripartite entanglement existent between three fields—signal, idler, and pump—from a nondegenerate optical parametric oscillator (NOPO) operating above the threshold. The special case of two cascaded NOPOs is studied, as it is shown that the five beams with very different frequencies are generated by NOPOA (one of the retained signal and idler beams, and the reflected pump beam) and NOPOB (the output signal and idler beams, and the reflected pump beam). These beams are theoretically demonstrated to be continuous variable (CV) entangled with each other by applying the positivity of the partially transposed criterion for the inseparability of multipartite CV entanglement. The symplectic eigenvalues of the partial transposition covariance matrix of the obtained optical entangled state are numerically calculated in terms of experimentally reachable system parameters. The optimal operation conditions to achieve high five-color entanglement are presented. As the cavity parameters and the nonlinear crystals of the two NOPOs can be chosen freely, the frequencies of the submodes in the entangled state thus are adjustable to match the transition frequencies of atoms or low loss fiber-optic communication window. The calculated results provide direct references for future experiment to generate multi-color entangled optical beams efficiently by means of NOPOs operating above the threshold.