Collective Spin Control by Quantum Coherent Optical Feedback

该奖项将支持开发一套新的工具，以控制和测量其行为受量子力学控制的物理系统。 该项目将把目前的单原子控制方法扩展到与大量原子相关联的多体系统。 基本目标是使用光作为量子总线来连接遥远的原子，从而获得对组合多体自旋的量子态的直接控制，而不需要单个原子直接相互作用。 这将通过相干光反馈来实现，其中光束穿过原子云以获取有关自旋的信息，然后在第二次通过中返回以相应地转换自旋量子态。 衡量成功的一个重要标准是人们可以减少（挤压）多体自旋的基本量子不确定性的程度。 自旋压缩在量子传感和量子计量学中有着直接的应用，并且可能是量子通信和计算的一种有价值的资源。 相干光反馈有可能产生压缩，随着时间和原子云的光密度的乘积呈指数级提高，并且相对于仅线性提高的现有方案可能是游戏规则改变者。 将进行实验，以确定在现实世界的情况下，包括退相干，光学损耗和缺陷的可能改善。 数值模拟表明，在计划中的第一代实验中，量子不确定性降低10倍应该是可行的。对复杂量子系统的控制的探索是目前广泛的物理学科所追求的巨大挑战。这一努力的动机是从量子多体物理模拟到量子限制计量学和量子信息处理的应用，所有这些应用都有一个共同的目标，即利用独特的量子特性来执行不可能完成的任务。 该项目将有助于量子信息科学的知识基础，并在这个高度跨学科的领域培养未来的科学家。 学生将参与该项目的各个方面，包括教育，研究和成果的传播。 该项目将成为NSF支持的量子信息与控制中心的基石，该中心位于亚利桑那大学光学科学学院和新墨西哥州大学物理与天文系。 每周视频会议，年度研究务虚会和联合参加会议将丰富教育经验，加强两个机构的初级和高级参与者之间的联系。

This NSF award will support the development of a new suite of tools to control and measure physical systems whose behavior is governed by quantum mechanics. The project will extend current methods for single atom control to a many-body system associated with a large collection of atoms. The fundamental goal is to use light as a quantum bus to connect distant atoms, and thus gain direct control over the quantum state of the combined many-body spin without the need for individual atoms to interact directly. This will be achieved through coherent optical feedback, wherein a light beam is passed through the atom cloud to pick up information about the spin, and then returned in a second pass to transform the spin quantum state accordingly. One important measure of success is the degree to which one can reduce (squeeze) the fundamental quantum uncertainty of the many-body spin. Spin squeezing has direct application in quantum sensing and metrology, and may be a valuable resource for quantum communication and computing. Coherent optical feedback has the potential to produce squeezing that improves exponentially with the product of time and optical density of the atom cloud, and could be a game changer relative to existing schemes that improve only linearly. Experiments will be performed to determine the possible improvement in a real-world situation that includes decoherence, optical losses and imperfections. Numerical simulation suggest that a factor of ten reduction in quantum uncertainty should be feasible in the planned first generation experiment.The quest for control of complex quantum systems is a grand challenge currently pursued across a broad spectrum of physics disciplines. The effort is motivated by applications that range from the simulation of quantum many-body physics to quantum-limited metrology and quantum information processing, all of which share the goal of harnessing uniquely quantum properties to perform tasks that are not otherwise possible. This project will contribute to the knowledge base of quantum information science, and to the training of future scientists in this highly interdisciplinary field. Students will be involved in all aspects of the project, including education, research, and the dissemination of results. The project will become a cornerstone of the NSF supported Center for Quantum Information and Control, co-located at the University of Arizona College of Optical Science and the University of New Mexico Department of Physics and Astronomy. Weekly video conferencing, an annual research retreat, and joint participation in conferences will enrich the educational experience and strengthen the connections between junior and senior participants at both institutions.