量子通信中的光量子态抗噪声处理研究

Quantum communication provides an absolutely secure way for information transmission from physical principles. Photonic quantum states are the information carriers for quantum communication. Depressing the influence from channel noise on photonic quantum states is necessary for secure quantum communication. It has some important applications in long-distance quantum communication. This project will study the methods for depressing the noise effect on photonic quantum states in quantum communication from the aspects of both theory and experiment, including self-error-rejecting transmission for photonic quantum states (an opposite mode for depressing the influence from noise) and entanglement purification (a passive one). First, we will investigate the self-error-rejecting transmission for polarizing photons in experiment, and explore the reliability of the assumption about collective noise in quantum channels. Second, we will investigate the one-step deterministic entanglement purification in experiment and find out the relation between the stability of spatial-mode quantum states and the distance for quantum communication. Third, we will give some different methods for depressing the influence of noise on photon systems in two or more degrees of freedom, including the self-error-rejecting transmission and hyper-entanglement purification. Fourth, based on the results from our experiments, we will design some models for heralded quantum repeaters which work in a fast way, by combining the opposite and the passive ways for depressing the noise influence. We hope that we will obtain some interesting outcomes on the ways for depressing the noise influence on photonic quantum states from this project. Also, we hope these outcomes have important applications in practical long-distance quantum communication.

量子通信利用量子力学原理实现物理原理上的安全通信。光量子态是量子通信中的信息传输载体。压制噪声对光量子态的不利影响是安全量子通信的必要条件，在中远程量子通信中有重要的应用价值。本项目从理论与实验两方面入手，深入研究量子通信中的光量子态抗噪声处理方法，包括主动模式的光量子态避错和被动模式的纠缠纯化，具体研究内容有：(1) 实验研究光子极化量子态自避错传输，探索联合噪声假设成立的近似条件；(2) 实验研究一步确定纠缠纯化，探索光子空间模式自由度量子态和相位稳定对通信距离的依赖程度；(3) 理论研究光子系统两自由度量子态抗噪声处理方法，包括两自由度光量子态的自避错传输方法和传输后的超纠缠纯化；(4) 结合主动与被动抗噪声方法，研究基于固态存储量子比特的快捷预报式量子中继器。通过本项目研究，力争在光量子态抗噪声处理方面有一些创新性的研究成果，推进它们在中长距离量子通信中的应用。

由于量子不可克隆定理，量子通讯具有经典通讯没有的安全性特征。光子系统具有多个可以当作量子比特的自由度，已有的模型通常基于光子某一个自由度进行量子计算。充分利用光子系统两个自由度进行量子通讯，需要的量子资源少、具有更强抵抗光子数损耗噪声的特征、相对而言更易于存储，因此基于光子系统两自由度的超并行量子通讯具有很好的研究价值。.我们的研究成果主要集中于以下三个方面：1、提出了可预报是否成功的量子中继器方案，在量子中继器实用中可通过预报剔除失败事件，提高中继效率。2、提出了超纠缠Bell态的完全性分析方案，具有节省资源、传输容量高等优点。3、提出了模拟任意哈密顿量和环境谱密度的量子开放系统动力学的量子模拟算法，具有严格求解、指数加快模拟速度的优点。.我们超额完成了预定的目标，已经发表论文50篇，其中SCI检索论文49篇，包含Nature出版集团期刊npj Quantum Information 1篇、美国物理学会期刊Physical Review A/E/Applied 10篇、美国光学学会期刊Optics Express 7篇、Annalen der Physik和Annals of Physics 各5篇。其中有2篇是本领域内的高被引论文。在国内重要学术会议上作学术报告24次，参加国内外学术会议52人次，培养博士毕业生9人、硕士毕业生10名。