CAREER: The Effect of State-Mixing Interactions on the Rydberg Excitation Blockade

本课题的目的是研究“里德堡激励阻滞”。原子将被冷却到极低的温度，并进入被称为里德伯态的高能态。在里德伯态中，最外层的电子（或原子带负电荷的部分）围绕原子核（或原子核心）以极大的轨道运行。由于这些大轨道，里德伯态原子的性质相对于自然状态或基态原子的性质被夸大了。其中一个性质是，当里德伯原子相隔很远时，它们之间会发生强烈的相互作用，即使它们没有净电荷。通常，当激光照射在一组原子上时，每个原子最外层的电子很容易被提升到里德伯态。然而，多个里德伯原子之间的相互作用导致这种激发被抑制，或“阻止”，并导致产生比其他情况下更少的里德伯原子。这种抑制激发可能有助于在计算机中使用单个原子作为“比特”（“中性原子量子计算”）。量子计算机有可能彻底改变数据安全和加密。本项目将重点关注使里德伯激励封锁函数不太有效的过程（状态混合相互作用）。本质上，如果有人试图用激光将原子置于给定的里德伯态，原子就会混合成其他态。这种混合“打破了封锁”，导致了大量的里德伯原子。本研究的目标是量化状态混合相互作用降低封锁效率的程度，了解导致混合的物理机制，并研究导致最佳激励封锁的实验参数。了解这些问题将使其他研究人员在开发量子计算机时能够以一种最大限度地减少不必要影响的方式使用封锁。该项目还包括一个重要的教育部分。PI将为从普通教育学生到高等物理学生等不同群体开发教育模块。该项目还将研究元认知练习对物理导论课堂解决问题表现的影响。所有的工作都将在一所以本科为主的大学完成，其中很大一部分是第一代大学生。里德伯激发阻滞是一种高激发原子之间的强相互作用抑制激光激发的过程，是最近一系列实验成果的核心。有人提出，在其他有利条件下，由Förster共振附近多粒子里德伯态之间的耦合引起的状态混合相互作用可能会损害抑制激发的有效性。然而，在实验中，封锁被破坏的程度是未知的，因为大量的状态混合总是伴随着改进的共振附近的封锁。在这个项目中，将使用磁光阱中铷里德伯原子的状态选择场电离光谱来量化状态混合降低封锁效率的程度。这项工作将导致更好地理解负责增强状态混合的物理机制。此外，该项目将包括对Förster共振附近最佳封锁的实验条件的系统研究。PI将为普通教育课程设计一个关于激光冷却和捕获的教育模块，以及一个关于在磁光阱中表征超冷原子云的高级实验室实验。

The goal of this project is to study the "Rydberg excitation blockade." Atoms will be cooled to extremely low temperatures and put into high energy states called Rydberg states. In Rydberg states the outermost electron (or the negatively charged component of an atom) travels in extremely large orbits around the nucleus (or the core of an atom). Because of these large orbits, atoms in Rydberg states have properties which are exaggerated relative to the properties of atoms in their natural, or ground state. One such property is that Rydberg atoms interact strongly with each other when separated by large distances, even though they have no net charge. Normally, when a laser is shined on a group of atoms, the outermost electron in each atom is readily promoted to Rydberg states. However, the interactions among multiple Rydberg atoms causes this excitation to be suppressed, or "blocked," and leads to the creation of fewer Rydberg atoms than would otherwise be created. This suppression of excitation may help enable the use of single atoms as the "bits" in computer ("neutral atom quantum computing"). Quantum computers have the potential to revolutionize data security and encryption. The present project will focus on processes which make the Rydberg excitation blockade function less effectively (state-mixing interactions). Essentially, if one tries to put atoms into a given Rydberg state using a laser, the atoms will mix into other states. This mixing "breaks the blockade" and leads to an undesirably large number of Rydberg atoms. The goals of the present research are to quantify the extent to which state mixing interactions reduce the blockade efficiency, to understand the physical mechanism which gives rise to the mixing, and to study the experimental parameters which lead to the best excitation blockade. Understanding these issues will allow other researchers to use the blockade in a way that minimizes unwanted effects when developing a quantum computer. The project also involves a significant educational component. The PI will develop educational modules for a diverse group, ranging from general education students to advanced physics students. The PI will also study the impact of metacognitive exercises on problem solving performance in the introductory physics classroom. All work will be done at a primarily undergraduate university with a significant fraction of first-generation college students.The Rydberg excitation blockade, a process whereby strong interactions among highly-excited atoms suppress laser excitation, has been at the heart of an array of recent experimental achievements. It has been suggested that state-mixing interactions, which result from couplings among multi-particle Rydberg states near a Förster resonance, may compromise the effectiveness of the excitation suppression under otherwise favorable conditions. Experimentally, however, the extent to which the blockade is compromised has been unknown, as large amounts of state mixing have always accompanied an improved blockade near resonance. In this project, the extent to which state-mixing reduces the blockade efficiency will be quantified using state-selective field ionization spectroscopy of rubidium Rydberg atoms in a magneto-optical trap. This work will lead to a better understanding of the physical mechanism responsible for enhanced state-mixing. Additionally, the project will include a systematic study of the experimental conditions for the best blockade near a Förster resonance. The PI will design an eduational module on laser cooling and trapping for a general education course as well as an advanced laboratory experiment on characterizing an ultracold atom cloud in a magneto optical trap.