Fundamental Quantum Optics in Hollow-Core Photonic Crystal Fibers

该计划旨在开发一种接近理想的材料介质，用于产生和操纵量子信息科学基础研究的非经典光态。理想是指在一个具有孤立自由度的系统中的光子-原子相互作用，这些自由度可以演化为相互纠缠，而不会与任何未受监测的辅助系统发生纠缠。正在开发的系统由限制在空芯光子晶体光纤（PCF）内部的超高密度氙气组成，该光纤可以在数米范围内引导紧密聚焦的光，增强光与物质的相互作用。该系统结合了几个突出的特性，使其成为理想的介质，用于光束之间的四波混频相互作用，包括光子对产生，模式纠缠，光频梳产生和孤子传播。作为一种流体（在温度16 ℃和压力57巴），近临界介质具有像气体一样的可变密度，但同时具有非常高的三阶光学非线性-接近固体石英玻璃，这是目前广泛使用的标准光纤介质。作为一种原子气体，二氧化硅具有可忽略的拉曼和布里渊散射水平，这严重阻碍了目前使用二氧化硅作为非线性光学介质的研究。在高密度量子阱系统中，我们期望在光子产生中看到降低的噪声信号和增强的纠缠，以及在频率梳产生和孤子传播中看到降低的噪声和增强的量子压缩，从而能够对这些现象进行更深入的基础研究。挑战包括设计Xe填充的PCF，以具有所需的色散特性，用于相位匹配感兴趣的非线性光学过程。这种新介质可以在光量子信息领域得到广泛应用，并可以改变我们执行全光量子态生成和操纵任务的能力。量子信息技术旨在以经典物理学技术无法实现的方式创建、存储、传输和处理信息。为此，我们需要光和物质之间的“理想相互作用”，在两个物理系统之间传递信息，而不会使信息部分“泄漏”到周围环境中。这种泄漏将破坏用于存储和处理量子信息的系统（原子或光子）的量子“完整性”。这种理想的相互作用是量子光学技术的核心，例如安全的长距离通信和使用光子态的量子计算。为了使这些技术发挥作用，我们需要接近理想的方法来制备、控制和操纵光子和光场的量子态。为此，我们正在开发一种独特的光学材料系统--将高密度氙气限制在空芯光纤的内部--它可以将紧密聚焦的光引导到几米之外，增强光与物质的相互作用。这样的一个系统被设计用来增强光与氙气的相互作用，氙气是诺贝尔气体中相互作用最强的一种，与标准气室中的室内压力气体相比，增强了几个数量级。当强激光穿过这种气体时，它的频谱可以以可预测的方式改变，产生许多新的频率，同时保持光量子态的“完整性”。这提供了创造具有不同频率的许多光波的“量子纠缠”状态的可能性。这种相互作用也可以产生量子孤子，量子孤子是在氙气中传播的光脉冲，而不会像光脉冲传播时通常发生的那样在时间上被拉伸。研究孤子可以检验最复杂的量子场论来描述光与物质的相互作用，量子光学提供了将研究与科学教育结合起来的绝佳机会。目前参与PI研究的博士生为NSF的GK-12计划做出了贡献，该计划将博士生与高中和中学配对，让他们的学生接触到研究作为职业的想法。近年来，高中生、本科生、硕士和博士生以及访问科学家都参与了这些小组的研究。学生还参加了一个新的科学素养计划在俄勒冈州，由PI共同指导的大学课程的共同讲师。

This program aims to develop a near-ideal material medium for generating and manipulating nonclassical states of light for fundamental studies in quantum information science. By ideal we mean photon-atom interactions in a system having isolated degrees of freedom that may evolve to become entangled among themselves without becoming entangled to any reservoir of unmonitored auxiliary systems. The system being developed is comprised of ultrahigh-density xenon gas confined to the interior of a hollow-core photonic crystal fiber (PCF), which can guide tightly focused light over several meters, enhancing the light-matter interaction. This system combines several outstanding properties, making it ideal for use as a medium for four-wave mixing interactions between light beams, including photon pair generation, mode entanglement, optical frequency comb generation, and soliton propagation. Being a fluid (at temperature 16 C and pressure 57 bar), near-critical Xe has variable density like a gas, but at the same time has a very high third-order optical nonlinearity -- approaching that of solid silica glass, which is the standard fiber-based medium now in wide use. Being an atomic gas, Xe has negligible levels of Raman and Brillouin scattering, which are severe impediments to current studies using silica as a nonlinear-optical medium. In the high-density Xe system we expect to see reduced noise signals and enhanced entanglement in photon generation, and reduced noise and enhanced quantum squeezing in frequency comb generation and soliton propagation, enabling deeper fundamental studies of these phenomena. Challenges include designing Xe-filled PCF to have the needed dispersion properties for phase matching the nonlinear-optical processes of interest. Such a new medium could find widespread use in the optical quantum-information community, and could transform our abilities to perform all-optical quantum-state generation and manipulation tasks.Quantum information technology aims to create, store, transmit, and process information in ways not possible using classical-physics-based techniques. For this we need "ideal interactions" between light and matter, with which to transfer information between two physical systems without having that information partially "leak" into the surroundings. Such leakage would destroy the quantum "integrity" of the systems (atoms or photons) being used to store and process the quantum information. Such ideal interactions are at the heart of proposed quantum optical technologies, such as secure long-distance communication and quantum computing using photon states. In order for such technologies to become useful, we need nearly ideal methods to prepare, control, and manipulate quantum states of photons and optical fields.For this purpose we are developing a unique optical material system -- high-density xenon gas confined to the interior of a hollow-core optical fiber -- which can guide tightly focused light over several meters, enhancing the light-matter interaction. Such a system is projected to enhance the interaction of light with xenon gas -- the most highly interacting of the nobel gases -- by several orders of magnitude compared with room-pressure gas in a standard gas cell. When intense laser light passes through such a gas, its frequency spectrum can be altered in a predictable way, generating many new frequencies, while maintaining the "integrity" of the quantum state of the light. This offers the possibility to create "quantum-entangled" states of many light waves having different frequencies. This interaction can also create quantum solitons, which are light pulses that travel in the xenon gas without becoming stretched in time, as usually occurs when light pulses propagate. Studying solitons can provide tests of the most sophisticated quantum field theories for describing the light-mater interaction.Quantum optics offers excellent opportunities to integrate research with science education. PhD students currently involved in the PI's research have contributed to the NSF's GK-12 Program, which pairs PhD students with high schools and middle schools, exposing their students to the idea of research as a career. High-school students, undergraduate students, Masters and PhD students, as well as visiting scientists, have all been involved in the groups' research in recent years. Students also participate as co-instructors of courses in a new Science Literacy Program at the University of Oregon, co-directed by the PI.