Quantum Feedback, Closed-Loop Magnetometry, and Quantum Nonlinear Dynamics at the Quantum/Classical Boundary

量子/经典边界的量子反馈、闭环磁力测量和量子非线性动力学

• 批准号: 1912417
• 负责人: Poul Jessen
• 金额: $ 57.54万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1912417&HistoricalAwards=false
• 关键词: Quantum; Feedback; Closed; Loop; Magnetometry

This work aims to help lay the foundation for new technologies that use quantum physics to out-perform conventional non-quantum devices, a situation referred to as "quantum supremacy". The first goal of this project is to borrow an element of conventional engineering known as the feedback loop (familiar from, e. g., the cruise control in a car), apply it to a manifestly quantum object (here, a collection of atoms trapped by a laser beam), and show that "quantum feedback" can greatly improve the sensitivity, speed, and reliability of magnetic sensors. From a basic science perspective, feedback control involves measurement and corrective action (e. g., measuring the speed of a car and increasing/decreasing engine power to keep the speed of the car reliably constant). In the quantum realm, this interplay between measurement and correction is fundamentally limited by the quantum uncertainty principle, according to which measurement also causes disturbance, which then limits the accuracy of the correction. The second goal of this project is to study this measurement/disturbance tradeoff in quantum feedback when controlling a physical system (again, atoms in a laser trap) subject to chaos, a scenario that is challenging even in conventional engineering.A recurrent theme in quantum metrology has been the use of continuous quantum measurement and feedback to construct adaptive measurement strategies that outperform their open-loop equivalents. One good example is the pioneering work of Wiseman on adaptive measurement strategies for homodyne phase estimation, along with related strategies for coherent state discrimination. In the early 2000's, Mabuchi and co-workers developed the theoretical framework for closed-loop strategies that use optical dispersive quantum nondemolition (QND) measurements and real-time feedback to create spin squeezing and perform magnetometry below the standard quantum limit (SQL), but were unable to implement these ideas in practice. The main objective of this project is to show that quantum feedback and closed-loop control of collective atomic spins is an experimentally viable idea with applications in quantum metrology and quantum simulation. Over the past few years the Principal Investigator has systematically solved many of the problems that plagued the early work, allowing significant deterministic squeezing of the collective angular momentum of an atomic ensemble, as well as a proof-of-principle demonstration of closed-loop control and magnetometry below the SQL. Building on these accomplishments, the goals of this project are (i) Further development of closed-loop magnetometry, and (ii) Exploration of a novel type of quantum nonlinear dynamics where the evolution of a quantum system is conditioned on the outcome of a time-continuous QND measurement. The latter provides an attractive platform for fundamental studies of the information gain/disturbance tradeoffs involved in real-time quantum feedback. It also provides access to new regimes of quantum simulation, and an opportunity to study long-standing issues related to quantum-classical correspondence in chaotic systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

这项工作旨在为使用量子物理学的新技术奠定基础，以超越传统的非量子设备，这种情况被称为“量子霸权”。这个项目的第一个目标是借用一个传统的工程元素，称为反馈回路（熟悉，e。例如，在一个实施例中，汽车中的巡航控制），将其应用于明显的量子物体（这里，被激光束捕获的原子集合），并表明“量子反馈”可以大大提高磁传感器的灵敏度，速度和可靠性。从基础科学的角度来看，反馈控制涉及测量和纠正措施（例如：例如，在一个实施例中，测量汽车的速度和增加/减少发动机功率以保持汽车的速度可靠地恒定）。在量子领域，测量和校正之间的相互作用从根本上受到量子不确定性原理的限制，根据该原理，测量也会引起干扰，从而限制校正的准确性。 该项目的第二个目标是研究当控制一个受混沌影响的物理系统（再次，激光阱中的原子）时，量子反馈中的测量/干扰权衡，这是一个即使在传统工程中也具有挑战性的场景。量子计量学中的一个反复出现的主题是使用连续量子测量和反馈来构建优于开环等效物的自适应测量策略。一个很好的例子是Wiseman关于零差相位估计的自适应测量策略沿着相干状态鉴别的相关策略的开创性工作。在21世纪初，Mabuchi及其同事开发了闭环策略的理论框架，该策略使用光学色散量子非破坏（QND）测量和实时反馈来创建自旋压缩并在标准量子极限（SQL）以下执行磁力测量，但无法在实践中实现这些想法。 该项目的主要目标是证明集体原子自旋的量子反馈和闭环控制是一个实验上可行的想法，可应用于量子计量学和量子模拟。在过去的几年里，首席研究员系统地解决了困扰早期工作的许多问题，允许原子系综集体角动量的显着确定性压缩，以及SQL下闭环控制和磁力学的原理证明。在这些成就的基础上，该项目的目标是（i）进一步开发闭环磁力测量，以及（ii）探索一种新型的量子非线性动力学，其中量子系统的演化取决于时间连续QND测量的结果。后者提供了一个有吸引力的平台，在实时量子反馈的信息增益/干扰权衡的基础研究。 该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Squeezing the angular momentum of an ensemble of complex multilevel atoms

压缩复杂多能级原子系综的角动量

• DOI: 10.1103/physreva.104.023710
• 发表时间: 2021
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Hemmer, D.;Montaño, E.;Baragiola, B. Q.;Norris, L. M.;Shojaee, E.;Deutsch, I. H.;Jessen, P. S.
• 通讯作者: Jessen, P. S.

Simulation of the complex dynamics of mean-field p -spin models using measurement-based quantum feedback control

使用基于测量的量子反馈控制模拟平均场 p 自旋模型的复杂动力学

• DOI: 10.1103/physreva.102.022610
• 发表时间: 2020
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: Muñoz-Arias, Manuel H.;Deutsch, Ivan H.;Jessen, Poul S.;Poggi, Pablo M.
• 通讯作者: Poggi, Pablo M.