CAREER: Matter-Wave Quantum Optics in Spin-Space in Ultracold Sodium Gases

该项目由原子、分子和光学物理实验计划和促进竞争性研究的既定计划（EPSCoR）共同资助。气体中原子之间的碰撞在我们周围随处可见，例如在我们每天呼吸的空气中。在室温下，碰撞是随机的，很难控制。通过将气体冷却到接近绝对零度（低于零下273摄氏度）的超冷温度，并将其困在真空室的中心，可以控制碰撞，并用于开发新技术，如杂质的量子限制传感器。超冷气体的行为就像一个单一的量子力学物体，一个物质波。碰撞仍然发生在物质波中，但它们现在以一种可预测的方式发生。在钠物质波中，可以通过微波辐射精确地控制碰撞。碰撞原子的行为就像小磁铁，由原子自旋的方向决定磁北极和磁南极。在碰撞过程中，原子会经历彼此的磁场并改变自旋方向。当它们改变方向时，原子自旋在量子水平上相互关联，这种现象被称为量子纠缠。当原子被用作传感器时，量子纠缠是有用的。所有纠缠在一起的原子对外部影响做出一致的反应，从而增加了传感器的灵敏度。该研究项目将使用钠物质波中的受控碰撞来研究量子增强传感和其他量子技术。该项目将研究杂质的作用，并将探索与纠缠光束实验相比的异同。这项研究将提高我们对现实条件下存在损耗和杂质的物质波的量子技术的实验理解。这对于开发强大的量子增强传感器，开发用于超冷气体的量子增强探测器，以及提高我们对如何在量子水平上控制物质波中的自旋的理解具有实际应用价值。本研究计划的目标是研究基于物质波量子工程的新一代量子技术，如用于高空间分辨率外场的量子增强传感器，用于测量低噪声超冷原子样品的量子增强探针，以及类似于光量子光学的相敏放大器等量子增强物质波器件。在长演化时间的限制下，通过微波修饰和射频控制原子钠的玻色-爱因斯坦凝聚体的自旋交换碰撞来控制物质波。在F=1的钠气体中进行自旋交换碰撞时，磁量子数m=0的原子对发生碰撞并变成磁量子数m=+/-1的原子对，反之亦然。这个过程产生的量子纠缠类似于光的四波混频。但是由于光子系统中没有哈密顿量的额外项，在原子系统中有重要的区别。在漫长的演化时间里，这些差异变得越来越重要，其中在钠玻色-爱因斯坦凝聚体中t30ms， c是自旋交换碰撞能量。它们会产生量子相变，从而产生大量的纠缠。基态只取决于气体是反铁磁性的（c0, Na），在那里它被大量纠缠，还是铁磁性的（c0, Rb），在那里它不被纠缠。该项目的目标是利用超冷钠的独特特性和物质波量子光学的最新技术进展，展示一个强大的、面向未来的物质波量子技术平台，为类似光子器件的物质波器件的广泛长期研究奠定基础。这是通过研究以下量子技术来实现的：a)在长演化时间限制下通过自旋混合干涉测量实现的量子增强传感，b)自旋种群的量子增强探测，c)外来多体态的量子态合成，d)杂质效应的量子模拟。该奖项反映了美国国家科学基金会的法定使命，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。

This project is jointly funded by the Atomic, Molecular, and Optical Physics Experiment Program, and the Established Program to Stimulate Competitive Research (EPSCoR).Collisions between atoms in gases happen all around us, for example in the air that we breathe every day. At room temperature, the collisions are random and very difficult to control. By cooling a gas to ultracold temperatures near absolute zero (below minus 273 degrees Celsius) and trapping it in the center of a vacuum chamber, collisions can be controlled and used to develop new technologies such as quantum-limited sensors for impurities. An ultracold gas behaves like a single quantum mechanical object, a matter wave. Collisions still take place in the matter wave, but they now happen in a predictable fashion. In a sodium matter wave, the collisions can be controlled precisely via microwave radiation. The colliding atoms behave like small magnets with magnetic north and south poles determined by the direction of their atomic spin. During collisions, atoms experience each other's magnetic fields and change their spin directions. As they change directions, the atomic spins become correlated with each other at the quantum level, a phenomenon known as quantum entanglement. Quantum entanglement is useful when atoms are used as sensors. All entangled atoms react to external influences in unison, increasing the sensitivity of a sensor. This research project will use controlled collisions in sodium matter waves to study quantum-enhanced sensing and other quantum technologies. This project will study the role of impurities and will also explore differences and similarities compared to experiments with entangled beams of light. The research will improve our experimental understanding of quantum technologies based on matter waves under realistic conditions, in the presence of loss and impurities. This has practical applications for development of robust quantum-enhanced sensors, for development of quantum-enhanced probes for ultracold gases, and for improving our understanding of how we can control spin in matter waves at the quantum level.The goal of this research program is to study a new generation of quantum technologies based on quantum engineering of matter-waves, such as quantum-enhanced sensors for external fields with high spatial resolution, quantum-enhanced probes of ultracold atomic samples to measure spin populations with reduced noise, and quantum-enhanced matter-wave devices such as phase-sensitive amplifiers, similar to those known from quantum optics with light. The control of matter-waves is exerted by microwave-dressing and RF control of spin-exchange collisions in a Bose-Einstein condensate of atomic sodium in the limit of long evolution times. During spin-exchange collisions in the F=1 sodium gas, pairs of atoms with magnetic quantum number m=0 collide and change into pairs with m=+/-1 and vice versa. This process generates quantum entanglement similar to four-wave mixing with light. But there are important differences in the atomic system due to extra terms in the Hamiltonian not present in the photonic system. These differences become increasingly important for long evolution times, t|h/c|, where t30 ms in a sodium Bose-Einstein condensate and c is the spin-exchange collisional energy. They give rise to quantum phase transitions that can generate massive entanglement. The ground state depends uniquely on whether the gas is antiferromagnetic (c0, Na), where it is massively entangled, or ferromagnetic (c0, Rb), where it is not entangled. The goal of this project is to make use of the unique features of ultracold sodium, and recent technological advances in matter-wave quantum optics, to demonstrate a robust and future-proof platform for matter-wave quantum technologies that will lay the groundwork for extensive long-term research on matter-wave devices similar to photonic devices. This is done by studying the following quantum technologies: a) quantum-enhanced sensing via spin-mixing interferometry in the long evolution time limit, b) quantum-enhanced probing of spin populations, c) quantum state synthesis of exotic many body states, and d) quantum simulation of the effect of impurities.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.