Physics and Applications of Cooperative Effects in Nonlinear and Quantum Optics

密集的原子集合可以显示出与稀薄样品中的集体现象根本不同的集体现象。一个例子是超辐射，即一组原子集体与特定的光场相互作用。虽然很久以前就认识到了这个话题，但在过去的几年里，这个话题变得越来越重要。许多基础研究领域，如量子信息科学，以及应用领域，如构建精确的原子钟，现在都利用密集系综的集体性质。密度效应可能是有害的。增加原子之间的相互作用强度可以破坏原子对外部刺激的相干反应，这是量子计算机或精确时钟所必需的。该项目的目标是(I)发现和了解依赖密度的集体效应及其后果，(Ii)研究以改善对集合的实验控制的方式减轻或隔离这些效应的方法，以及(Iii)研究这种效应可以使新技术成为可能的各种方式。关于合作介质中的集体效应的基本问题将被研究，例如：超辐射效应取决于密度还是光学深度？交流互动的作用究竟是什么？驱动合作系统的特殊之处在哪里？超辐射是完全由成对关联描述的吗？对于哪些系统需要其他近似？为了实现这些目标，将开发新的解析和数值方法。此外，这个项目将研究的特殊效应包括诱导和自发的集体谱线移动，自旋和光场的“压缩”和纠缠。此外，动态卡西米尔效应的统计和非线性将与超辐射系统的集体效应进行比较。这些项目中的大多数将包括与实验工作的合作。

A dense collection of atoms can display collective phenomena which are fundamentally different from those in dilute samples. An example is super-radiance, where an ensemble of atoms collectively interacts with a specific light field. While recognized long ago, this topic has gained importance over the last few years. Many areas of fundamental research, such as quantum information science, and of applications, such as the construction of accurate atomic clocks, now utilize collective properties of dense ensembles. Density effects can be detrimental. Increasing the interaction strength between atoms can destroy the coherent response of the atoms to external stimuli, which is necessary for quantum computers or precise clocks. The goal of this project is to (i) find and understand density-dependent collective effects and their consequences, (ii) to investigate methods to either mitigate or isolate the effects in a way to improve experimental control of the ensembles, and (iii) to research the various ways in which such effects can enable new technologies. Basic questions will be studied regarding collective effects in cooperative media, such as: Do super-radiant effects depend on density or optical depth? What exactly is the role of the exchange interaction? What makes driven cooperative systems special? Is super-radiance fully described by pairwise correlations, and for which systems are other approximations needed? In order to achieve these goals, new analytical and numerical methods will be developed. In addition, the particular effects that will be investigated in this project include induced and spontaneous collective line shifts, spin and light field "squeezing" and entanglement. In addition, statistics and nonlinearities of the dynamic Casimir effect will be compared to the collective effects of super-radiant systems. Most of these projects will include collaboration with experimental efforts.