Ultrashort Single Photon Generation via Conditional Excitation of an Atomic Barium Ensemble

该项目探索了原子钡系综作为纯超短单光子的可扩展源的使用，以及远距离光子、原子系综和两者组合之间各种类型纠缠的创建、保存和检测。通过将非共振超短激光脉冲应用于温暖的原子钡蒸气，我们在原子系综中产生集体激发，称为自旋波，同时产生量子电磁激发，即光子。光子的探测表明一个成功的事件和物质中自旋波的存在。这种长寿命的集体激发可以通过施加另一个超短脉冲在稍后所需的时间转换成纯波包中的超短单光子。通过结合多个原子集成，我们能够同步创建多个纯超短且相同的光子，这是高比特率量子计算和通信应用的基本要求。相关场的宽带宽允许我们研究产生的光子和原子激发之间非经典相关性的光谱特性，增加了我们在量子水平上控制光-物质相互作用特性的理解和能力。本项目的工作提供并演示了一种产生适合高速量子通信和计算操作的光子的方法，例如纠缠交换和贝尔态测量。这些应用是量子隐形传态、量子密码学和贝尔不等式检测等协议的重要组成部分。通过本项目对研究生和本科生进行超快量子光学和原子物理的实验和理论训练。该项目是特拉华大学本科教程的基础，旨在激励和提高学生对量子力学的理解。

This project explores the use of an atomic barium ensemble as a scalable source of pure ultrashort single photons and the creation, preservation and detection of various types of entanglement between distant photons, atomic ensembles and combinations of both. By applying an off-resonant ultrashort laser pulse to warm atomic barium vapor, we generate a collective excitation in the atomic ensemble, called a spin wave, together with a quantum of electromagnetic excitation, i.e. a photon. The detection of the photon signals a successful event and the presence of the spin wave in the matter. This long-lived collective excitation can be converted into an ultrashort single photon in a pure wave-packet at a later desired time by applying another ultrashort pulse. By combining numerous atomic ensembles, we are able to create multiple pure ultrashort and identical photons synchronously, an essential requirement for high bit-rate quantum computation and communication applications. The broad bandwidth of the involved fields permits us to study the spectral properties of nonclassical correlations between the created photon and the atomic excitation, adding to our understanding and ability to control the properties of light-matter interaction at the quantum level.The work of this project provides and demonstrates a method to generate photons suitable for high-speed quantum communication and computation operations, such as entanglement swapping and Bell state measurements. These applications are essential components of protocols such as quantum teleportation, quantum cryptography and Bell inequality detection. Through this project graduate and undergraduate students are trained in experimental and theoretical ultrafast quantum optics and atomic physics. The project serves as the basis for an undergraduate tutorial at the University of Delaware to motivate and improve student understanding of quantum mechanics.