Issues of Continuous Quantum Measurements and Feedback Control

连续量子测量和反馈控制问题

• 批准号: 1401151
• 负责人: Juha Javanainen
• 金额: $ 18万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1401151&HistoricalAwards=false
• 关键词: Issues; Continuous; Quantum; Measurements; Feedback

This work is on the theoretical physics of measurements in quantum mechanical systems. There are two components to this research. First, light scattering is used as a method to measure the properties of an atomic system. At the true quantum level, light arrives at a detector as individual photon counts. Light scattering in a model system is simulated exactly, and then simulation results will be used to develop statistical techniques to extract information about the system even if there are only a few isolated photon counts. In a related issue, to enable full transfer of quantum mechanical information between light and a collection of atoms, the atomic sample should ideally be dense and cold. Massive numerical simulations of light propagation in a cold dense gas have shown that the current understanding of such systems is flawed. New principles will be formulated that govern this case. This work is pure basic research, and the final aim is to help build the science basis for future quantum technologies.A Bose-Einstein condensate in a double-well potential is used as a generic example to study light scattering from a material sample. The light is assumed to be monitored using detectors capable of single-photon resolution. The quantum mechanics of the joint light-matter-detector system is solved exactly using quantum trajectory simulations. A Bayesian inference is developed as a method to extract the maximum possible amount of information about the atoms from the observed photon counts. The immediate aim is to devise repeated and correlated photon counting measurements for monitoring and feedback control of quantum systems. More generally, light scattering is the method to monitor not only double-well condensates, but also probably the majority of atomic systems under continuous observation. To reach a resolution at the level of a single quantum, the sample has to be optically thick. The potentially high densities and the low temperatures beneficial for quantum coherence will bring in the possibility of cooperative response of the atoms to light. Cooperative light-atom interaction using classical-electrodynamics simulations of light propagation in a medium of point dipoles will be studied. The objective is to find out how the cooperative response alters the results of light scattering experiments.

这项工作是在量子力学系统的测量理论物理。这项研究有两个组成部分。首先，光散射被用作测量原子系统性质的方法。在真正的量子水平上，光以单个光子计数的方式到达探测器。精确地模拟了模型系统中的光散射，然后将模拟结果用于开发统计技术，以提取有关系统的信息，即使只有几个孤立的光子计数。在一个相关的问题中，为了实现光和原子集合之间的量子力学信息的完全传递，原子样品理想地应该是致密和冷的。光在冷稠密气体中传播的大量数值模拟表明，目前对这种系统的理解是有缺陷的。将制定新的原则来管理这种情况。本研究是纯基础研究，最终目的是为未来的量子技术奠定科学基础。以双势阱中的玻色-爱因斯坦凝聚体为例，研究了材料样品的光散射。假设使用能够单光子分辨率的探测器来监测光。采用量子轨道模拟方法，精确求解了光-物质-探测器联合系统的量子力学问题。贝叶斯推理是一种从观测到的光子计数中提取最大可能量的原子信息的方法。当前的目标是设计重复和相关的光子计数测量，用于量子系统的监测和反馈控制。更一般地说，光散射不仅是监测双阱冷凝物的方法，而且可能是监测连续观察下的大多数原子系统的方法。为了达到单量子水平的分辨率，样品必须具有光学厚度。潜在的高密度和有利于量子相干的低温将带来原子对光的合作响应的可能性。利用经典电动力学方法模拟光在点偶极子介质中的传播，研究光与原子的相互作用。目的是找出如何合作的响应改变光散射实验的结果。