Single-Photon Subradiance, Superradiance, and Emergent Cooperativity in Cold Atomic Matter

冷原子物质中的单光子次辐射、超辐射和突现协同性

• 批准号: 1606743
• 负责人: Charles Sukenik
• 金额: $ 45.85万
• 依托单位: Old Dominion University Research Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-08-15 至 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1606743&HistoricalAwards=false
• 关键词: Single; Photon; Subradiance; Superradiance; Emergent

The merger of quantum optics and cold atom physics has revolutionized several areas of scientific and technical development. Quantum optics is the field of study of particles of light, photons, and their interaction with matter. Cold atom physics is the investigation of cold atoms and their interaction with light and with other matter. (Atoms can be cooled to as low a temperature as about 50 picokelvin, a thrillionth of a degree above absolute zero. For comparison, the cold near vacuum of outer space is about 3 Kelvin, and room temperature is about 300 Kelvin.) These joined scientific areas have led to improved atomic clocks, development of sensors of magnetic and electric fields, measurements of gravitational forces, and rotational motion, to name a few. At the same time, entirely new areas of practical and fundamental investigation been developed, including quantum simulations of materials and plasma physics, and the dynamic research area of quantum informatics. This project is focused on experimental and theoretical study of single-photon super radiance and sub radiance in cold atomic gases. These are emergent effects, which do not occur for single atoms by themselves, but require cooperative interactions among a group of atoms. In super radiance, light emitted from a gas of cold atoms does so at a rate much faster than from a single atom. The light also is emitted in a narrow cone and behaves like a jet of photons. In sub radiance, the converse is true; light emerges on the average in all directions, at a very slow rate, and can even be stored for a long period of time in the gas. These fundamental quantum optical processes are accompanied by a shift of the frequency (or wavelength) and loss of the purity of the color of the emitted light. As such, these effects can have a negative influence on the performance of atomic clocks or other precision sensors. Thorough understanding of super and sub radiance, one of the main goals of this project, is thus essential to optimizing the operation of these devices. On the other hand, it is possible to use these effects to advantage to form the basis of a single photon memory for light. In this case, a photon is taken up in a super radiant state, and quickly transferred to a long lived sub radiant configuration. At a later controllable time the atomic gas can be switched back to a super radiant state, in which the stored photon is reemitted into its original mode. The main scientific focus of this project is to study and understand the phenomenology of single photon super and sub radiance in cold atomic gases, and to learn about the impact of these processes on quantum sensors, and possible applications to single photon quantum memories. In the project, a dense and cold sample of cold rubidium atoms is optically prepared and interrogated by a narrow-band and near-resonance probe beam. The atomic sample is elliptical with large aspect ratio, and is typically optically excited along the long axis. This geometry has been shown theoretically to lead to an enhanced collective Lamb frequency shift in the forward scattered light. The probe beam is prepared as a temporally short pulse for time resolved studies and is considerably longer and spectrally narrower for frequency shift measurements. Enhanced and rapid emission is observed in the near-forward direction, while both super radiant and sub radiant emission is studied in an off-axis configuration. In initial studies, single photon super radiance is observed; the rate for the process is found to increase linearly with increasing optical depth, characteristic of a cooperative process. A spectral shift of the resonance to lower frequency, with linear dependence on the optical depth, has also been measured. Current and developing aspects of the project include study of (a) superradiant pulse propagation effects in the dense gas. These can modify the linear cooperative scaling and limit the practical applications; (b) few-body collective effects including two-body super and sub radiance; (c) the influence of inhomogeneous broadening process, such as Doppler broadening and trap induced light shifts on mixing and controlled coupling between super and sub radiant configurations.

量子光学和冷原子物理学的合并彻底改变了科学和技术发展的几个领域。 量子光学器件是光，光子颗粒及其与物质相互作用的研究领域。 冷原子物理学是对冷原子的研究及其与光和其他物质的相互作用。 （原子可以冷却至高于50 picokelvin的温度，高于绝对零以上的刺激性。为了进行比较，外层空间的近近距离真空约为3 kelvin，室温约为300 kelvin。）这些连接的科学领域已导致了磁性和电力型和电力型的旋转力和旋转量的磁性和旋转的旋转，并构成了旋转的速度和旋转。 同时，开发了全新的实用和基本调查领域，包括材料和等离子体物理学的量子模拟，以及量子信息学的动态研究领域。 该项目的重点是对冷原子气体中单光子超级辐射和亚辐射的实验和理论研究。 这些是紧急效应，单个原子本身不会发生，而是需要一组原子之间的合作相互作用。 在超级辐射中，从冷原子气体发出的光的速度比单个原子快得多。 光还以狭窄的锥体发射，表现得像光子的喷射。 在子辐射中，相反的是真实的。光平均以非常缓慢的速度出现，甚至可以在天然气中储存很长时间。 这些基本的量子光学过程伴随着频率（或波长）的变化以及发射光的颜色纯度的丧失。 因此，这些影响可能会对原子钟或其他精确传感器的性能产生负面影响。 因此，对该项目的主要目标之一，对超级和子辐射的透彻理解对于优化这些设备的操作至关重要。 另一方面，可以利用这些效果来构成光子记忆的基础。 在这种情况下，以超辐射状态接收光子，并迅速转移到长期寿命的子辐射构型中。 在后来的可控时间，原子气可以转回超辐射状态，其中将存储的光子重新置于其原始模式中。 该项目的主要科学重点是研究和了解冷原子气体中单光子超级和子辐射的现象学，并了解这些过程对量子传感器的影响，以及对单个光子量子记忆的可能应用。在该项目中，冷rubium原子的致密和冷样品是通过狭窄带和近谐振探针束进行光学制备和审问的。 原子样品是椭圆形的，具有较大的纵横比，通常在长轴上光学兴奋。 从理论上讲，这种几何形状已导致向前散射光中增强的集体羊肉频移。 探针梁作为时间上的脉冲进行准备，以进行时间分辨研究，并且在频移测量方面较长，并且在频谱上更窄。 在近乎前进的方向上观察到增强和快速的发射，而超辐射和子辐射发射都以外轴构型进行了研究。在最初的研究中，观察到单个光子超辐射。发现该过程的速率随着光学深度的增加，是合作过程的特征。 还测量了共振到较低频率的光谱移位，并依赖于光学深度。 该项目的当前和发展方面包括对（a）致密气体中的超级脉冲传播效应的研究。这些可以修改线性合作缩放并限制实际应用； （b）几个体制的集体效应，包括两体超级和子辐射； （c）不均匀扩展过程的影响，例如多普勒拓宽和陷阱引起的光转移对超级和亚辐射构型之间的混合和受控耦合。