一种生成质量最优路径纠缠微波信号的压缩参量选择方法

An approach to selecting the optimal squeezed parameter for generating path entangled microwave signal

介绍了路径纠缠微波及其生成原理,将生成信号以量子力学算符的形式表示,并在光子数态表象下展开,定性地给出了生成信号与压缩参量之间的关系.提出了一种路径纠缠微波信号质量评价方法,即通过信号中纠缠微波光子总数的期望值表征信号的纠缠度,间接实现对信号质量的评价.基于这种信号质量评价方法,提出了一种生成质量最优路径纠缠微波信号的压缩参量选取方法:在近似确定有效纠缠微波光子数的前提下,找出生成不同微波光子数纠缠概率最大时的一组压缩参量值,进而得出各个压缩参量值所对应的一组纠缠微波光子总数的期望值,其中的最大值对应的压缩参量值即为生成质量最优信号所要选择的压缩参量值.通过理论分析,发现路径纠缠微波信号质量由压缩参量决定,且只与压缩幅有关,而与压缩角无关.仿真实验结果表明,在纠缠微波光子数的最大有效值取为"26"时,纠缠微波光子总数期望值的最大值对应的压缩幅值为1.77,即压缩幅取此值时所得到的路径纠缠微波信号质量最佳,仿真结果表明该方法是有效的.本文的研究为路径纠缠微波在实验研究和实际应用中如何生成高质量信号的问题提供了思路.

Quantum information theory can improve the performances of the classical information techniques by utilizing the entangled state of electromagnetic field. Path entangled microwave signal distributes its entangled states between spatially separated subsystems of an information system, which can be widely applied to quantum information technology in the future. Currently, there are only several reports on path entangled microwave signal generation. Therefore, the quality of path entangled microwave signal is far from satisfactory. In order to improve the quality of path entangled microwave signal further, we make a discussion about the factors that affect the quality of it and design a quality evaluation scheme for it. Based on the designed quality evaluation scheme, an optimal squeezed parameter selection method is suggested. Firstly, the generation principle of path entangled I^dcrowave signal is briefly introduced, and the generated signal is denoted as quantum mechanics operator in the Fock state representation. In the meantime, the qualitative relationship between generated signal and the squeezed parameter is determined. Secondly, a quality evaluation method for path entangled microwave signal is proposed： the quality of generated signal is evaluated by comparing with the expectation value of the entangled microwave photon number which reflects the degree of quantum entanglement. Finally, an approach to selecting the optimal squeezed parameter for generating the path entangled microwave signals is proposed based on the quality evaluation method. The process of it is as follows： an array of squeezed parameters which achieve the highest entanglement probability of different microwave photons is acquired under the premise that the maximal effective number of entangled microwave photons is set to be a certain value. Then an array of expectation values of number of entangled microwave photons corresponding to these squeeze parameters is acquired, and the squeezed parameter corresponding to the largest expectation value is what we are searching for. Through theoretical analysis, we draw a conclusion that the quality of path entangled microwave signal is determined by squeezed parameter. Accurately, it is related to the squeezed degree, but unrelated to the squeezed angle. From simulations, we find that the maximal expectation value of the total number of entangled microwave photons is 3.77 when the simulation proceeds on condition that the maximal number of effective entangled microwave photons is set to be 26. And its corresponding squeezed degree value is 1.77, which means that the optimal path entangled microwave signal can be generated when we set the value of squeezed degree to be 1.77. And our method is proved effective by the simulation results. We provide an original idea on generating high-quality path entangled microwave signals for its experiments and applications.