Expanding the Toolbox for Quantum Control of Atomic Qudits

该项目使用激光冷却铯原子的超精细自由度作为开发和测试量子控制和测量新工具的试验平台。 编码在原子基态超精细态中的量子比特和量子点（d能级量子系统）对于这样的工作特别有用，因为它们提供了很长的相干时间，可以用射频和微波场进行相干操纵，并且可以用光场进行微弱或强烈的探测。工作重点将放在两个密切相关的研究领域。第一个涉及具有复杂内部结构的量子系统的控制和测量，其主要目标是实现对16维超精细基流形中编码的量子比特和量子位的幺正控制，探索制备任意混合态和实现完全正映射的方法，以及改进或开发基于弱测量并通过诸如压缩感测的新思想增强的用于量子状态和过程层析成像的新协议。 第二个重点领域涉及真实的世界平台上的量子控制，其主要目标是改进和扩展非均匀加宽量子系统中的鲁棒量子控制工具，并将其应用于光学偶极阱和光学表面阱中的原子。该研究主要是实验性的，但也将进行数值模拟和更正式的理论研究。量子信息科学（QIS）领域的动力来自于对计算，通信和超精密测量的变革性方法的承诺。它还激发了对物理学中的老问题和未解决问题的新思考方式，并在研究理想化理论模型的现实适用性的量子模拟中发挥了作用。QIS现在在许多背景下被追求，包括纳米制造的凝聚态系统，冷原子和离子，线性和非线性光学系统，以及它们的各种混合物。虽然细节因物理学而异，但QIS最基本的挑战之一是普遍的：必须在定义良好的初始状态下准备相关的量子系统，通过复杂的演化驱动它，并通过测量访问最终状态。这样，在一个平台上开发的许多工具可以应用于另一个平台。 该项目将使用冷原子作为控制具有两个以上能级的量子系统的试验台。 由此产生的工具箱可能是有用的，也许是必要的，在许多实现中，量子信息的载体具有复杂的内部结构。该项目还将有助于在QIS高度跨学科领域培训未来的科学家。 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。 该项目是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 project uses the hyperfine degrees of freedom of laser cooled cesium atoms as a testbed on which to develop and test new tools for quantum control and measurement. Qubits and qudits (d-level quantum systems) encoded in atomic ground hyperfine states are especially useful for such work because they provide long coherence times, can be coherently manipulated with radiofrequency and microwave fields, and can be probed weakly or strongly with optical fields. Efforts will be focused on two closely related areas of research. The first concerns control and measurement of quantum systems with complex internal structure, and has as its primary objectives to implement unitary control of qubits and qudits encoded in the 16-dimensional hyperfine ground manifold, to explore methods to prepare arbitrary mixed states and implement completely positive maps, and to improve or develop new protocols for quantum state and process tomography based on weak measurement and augmented by new ideas such as compressed sensing. The second focus area relates to quantum control on real world platforms, and has as its primary goals to improve and extend tools for robust qudit control in inhomogeneously broadened quantum systems, and to apply these to atoms in optical dipole traps and optical nanofiber surface traps. The research is primarily experimental, but numerical simulation and more formal theoretical study will also be undertaken.The field of Quantum Information Science (QIS) is motivated by the promise of transformative approaches to computation, communication, and ultra-precise measurement. It has also inspired new ways of thinking about old problems and unresolved issues in physics, and played a role in quantum simulations that study the real-world applicability of idealized theoretical models. QIS is now pursued in many contexts, including nanofabricated condensed matter systems, cold atoms and ions, linear and nonlinear optical systems, and various hybrids thereof. Though details vary with the physics at hand, one of the most fundamental challenges of QIS is universal: one must prepare the relevant quantum system in a well defined initial state, drive it though a complex evolution, and access the final state through measurement. In doing so, many of the tools developed on one platform can be applied to another. This project will use cold atoms as a testbed for control of quantum systems that have more than two levels. The resulting toolbox is likely to be useful and perhaps essential in the many implementations where carriers of quantum information have complex internal structure. The project will also contribute to the training of future scientists in the highly interdisciplinary field of QIS. Students will be involved in all aspects of the project, including education, research, and the dissemination of results. The project is 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.