微波连续变量极化纠缠

极化微波作为当前被广泛应用的信息载体,具有许多独特的优势.随着超导技术的发展,量子微波技术逐渐兴起,将量子纠缠应用于极化微波将具有广阔的应用前景.本文阐述了连续变量极化纠缠的原理,提出了极化纠缠微波方案并进行了仿真分析,利用归一化的不可分度I作为判据,分析了在整个约瑟夫森混合器100 MHz工作带宽内斯托克斯参量的不可分度I(S_1,S_2),I(S_2,S_3),并进一步分析了I分别与压缩度r、振幅比值Q的关系,发现I(S_1,S_2),I(S_2,S_3)分别对振幅比值Q、压缩度r的变化敏感,且在本文研究的条件下I(S_1,S_2)始终大于1,I(S_2,S_3)始终小于1,斯托克斯参量S_2,S_3构成不可分态,方案产生的两个微波信号E_a和E_b存在二组分极化纠缠,最佳纠缠出现在70 MHz附近,此时I(S_2,S_3)取得最小值0.25.

Continuous variable polarization entanglement in microwave domain

As a widely utilized information carrier, polarization microwave shows plenty of merits. Quantum microwave is booming gradually due to the development of superconducting technology, which makes it a promising potential to apply quantum entanglement to polarization microwave. In this paper, we introduce the concept of continuous variable polarization entanglement. Meanwhile, a scheme of polarization entanglement in microwave domain is proposed and simulated. The detail derivations are given and discussed. Polarization entangled microwaves are prepared by combining quadrature entangled signals and strong coherent signals on polarization beam splitters, and quadrature entangled signals are prepared by utilizing Josephson mixer. In order to probe the polarization entanglement between output signals, inseparability of Stokes vectors \$I({\hat S_1},{\hat S_2})$\ and \$I({\hat S_2},{\hat S_3})$\, is analyzed in 100 MHz operation bandwidth of Josephson mixer. The relation between inseparability I and squeezing degree r and between inseparability I and amplitude ratio Q are analyzed respectively. The results show that \$I({\hat S_1},{\hat S_2})$\ is sensitive to the variation of Q, while \$I({\hat S_2},{\hat S_3})$\ is sensitive to the change of r. The physical reasons for these results are explored and discussed. Apart from these, \$I({\hat S_1},{\hat S_2})$\ remains its value above 1 under the condition in this paper, but on the contrary, \$I({\hat S_2},{\hat S_3})$\ keeps its value well below 1. It proves that \${\hat S_2}$\ and \${\hat S_3}$\ of Stokes vectors are inseparable from each other, thus output signals \${\hat E_a}$\ and \${\hat E_b}$\ of our scheme exhibit bipartite entanglement. The best entanglement appears nearly at about 70 MHz, at this point the minimum \$I({\hat S_2},{\hat S_3})$\ value is 0.25.