基于时间空间多路复用的多光子纠缠源制备实验研究

The generation and manipulation of multiphoton entangled states is significant in the quantum information science. So far the main method to generate entangled photon pairs arises from spontaneous parametric down-conversion (SPDC) process, which has the advantages of convenience, high fidelity and mature technology. However, a fatal flaw of SPDC is that it belongs to the stochastic process, thus the multiphoton counting rates decreases exponentially with the increasing photon number. In addition, the high-order multiphoton noise due to the stochastic nature is also the main noise in the multiphoton experiments. How to increase the signal intensity and lower the high-order noise is the urgent issue for multiphoton experiments. In this project, we apply the temporal and spatial multiplexing method to the multiphoton entangled state generation by analogy with the development model of the modern computer’s CPU. Namely, by increasing the pump pulse repetition frequency and building more SPDC sources, which is hopeful to improve the multiphoton counting rates greatly.

多光子纠缠态的制备与操纵对量子信息科学具有重要意义。自发参量下转换是目前产生光子纠缠的主要手段，具有方便快捷、保真度高、技术成熟等优势。而自发参量下转换的一个致命缺陷就是它属于随机过程，制备多光子的计数率随光子数增加呈指数衰减。此外由于随机过程所导致的高阶多光子项噪声也是目前多光子实验的主要噪声。如何提高信号强度，并压低高阶噪声是目前多光子实验亟待解决的问题。在该项目中，我们类比经典计算机CPU的发展模式，将时间空间多路复用方案应用于多光子纠缠态的制备，即提高泵浦光脉冲的重复频率和搭建更多的纠缠源，有望使多光子计数率得到大幅度的提升。

多光子纠缠态的制备对光量子信息处理具有重要意义。自发参量下转换是目前产生多光子纠缠的主要手段，具有方便快捷、保真度高、技术成熟等优点。而自发参量下转换的一个致命缺陷就是它属于随机过程，制备多光子的计数率随光子数增加呈指数衰减。此外由于随机过程所导致的高阶多光子项噪声也是目前多光子实验的主要噪声。在该项目中，我们提出将时间空间多路复用方案应用于多光子纠缠态的制备，即提高泵浦光脉冲的重复频率和搭建更多的纠缠源，有望在大幅度提高多光子计数的同时压低高阶多光子噪声。经过本项目的实施，我们通过自行设计的蝶形腔将飞秒激光器的重复频率提高了5倍，并在实验中直接观测到了提高重复频率后对高阶多光子噪声的抑制作用。同时我们还构建了一套多光子实验的理论模型用于分析高阶多光子噪声对纠缠态保真度的影响。

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