利用多模光场实现多个原子团的纠缠

Entanglement is a profound concept in Quantum Physics, and plays a key role in the research of quantum information processing. As an application, quantum network is a key ingredient of the new technologies such as quantum distributed computation, quantum information communication, and quantum teleportation. Quantum network is composed of quantum nodes and the channels that interconnect between the nodes. In general, quantum memories work as the quantum nodes, while quantum channels transmit the flying light signals. For sake of practical reasons, large-scale quantum networks are of great interest in recent years. Entangling a large number of memories (ensembles) is a necessity of building such a network. Conventionally, the network can be built by applying the entanglement swapping technique, step by step. Such attempt is not promising in the case of high dimensionality. The aim of this research project is to find a new way to build a large-scale quantum network simultaneously, taking advantage of the multimodal character of light fields, and by transferring the entanglement from the optical components to the atomic components during the light-matter interaction with corresponding optical modes. In this project, the mechanism on the entanglement transferring between the multimode lights and the ensembles located in different geometries will be fully considered, the means to enhance the transferring efficiency will be discussed, and the entanglement fidelity will be analysed. The expected results of this project may bring a new light to quantum information processing and quantum control.

纠缠是量子物理的基本概念，在量子信息研究中起着核心的作用。作为其应用，量子网络在量子分布式计算、量子信息传输、量子隐形传态等新技术里都起着重要的作用。量子网络由量子节点以及连接节点的量子通道构成。一般而言，节点往往由量子存储器来实现，量子通道则传递光信号。出于实用的需要，大尺度的量子网络一直是学术关注的热点。建立大尺度量子网络需纠缠巨大数目的存储器(原子团)，传统的方法是用纠缠交换的方式来逐步实现，这方法并不很实用。本项目重点研究一种新的、同时纠缠多个原子团的方案：从量子光场的多模特性出发，通过对光学模式的选择操控来实现不同模式的光场分量与原子团的相互耦合，进而利用多模光场的纠缠特性来实现多个原子团的纠缠。本项目还将探索光场与不同空间位形原子团间纠缠的相互转移机理，及增强转移的方式，最后分析纠缠的保真度。本项目的预期成果对量子信息处理以及量子调控提供了一种新的思路和途径。

多体/多模式纠缠是量子信息与量子技术的重要组成部分。多模光场与原子系综发生作用产生多体/多模纠缠的方案受到学界广泛关注。本研究通过理论建模的方式，讨论了多模式光场与多个原子团相互作用背景下，纠缠，压缩等量子特性在四波混频等非线性光学过程中的产生与探测，以及具有超宽光谱的量子态对物质的相干控制。通过研究，我们清楚理解了相互作用的机制，得到多个原子系综与光相互作用后系统的多体纠缠特性；发现在单个系综中，可以对多模光场的纠缠进行扩展；利用光学钟跃迁能级，我们找到了一个稳定的四波混频发生载体。最后，我们研究了超宽光谱对系综的相干控制。这些理论结果发现为后续的研究打下基础，并对相关实验具有指导意义。