Interacting Bose-Einstein Condensates: Tunneling, Localization, and Beyond Mean-Field

相互作用的玻色-爱因斯坦凝聚态：隧道效应、局域化以及超越平均场

• 批准号: 1102515
• 负责人: Randall Hulet
• 金额: $ 57万
• 依托单位: William Marsh Rice University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-15 至 2014-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1102515&HistoricalAwards=false
• 关键词: Interacting; Bose; Einstein; Condensates; Tunneling

Lithium atoms exhibit extraordinarily broad Feshbach resonances. The Feshbach resonance for the lowest hyperfine sublevel of Li-7 extends over a range of approximately 200 Gauss (G), where it goes through a zero crossing with a slope of only 0.1 ao/G, where ao is the Bohr radius. Our work exploits the properties of this Feshbach resonance to study bosons with attractive, weak, or very strong interactions.The creation of bright matter wave solitons, previously demonstrated with weakly attracting Li-7 atoms, enables the exploration of fundamental quantum phenomena. We study single particle tunneling by causing the soliton to execute dipole oscillations in a one-dimensional optical trap in the presence of a central barrier formed from a light sheet. This system may show a remarkable coherent recombination that could form the basis for a bright matter wave soliton interferometer. Longer term goals are to work towards true macroscopic quantum tunneling in order to create a Schrödinger Cat state.Our second project is study of the effect of a disordered potential, created from optical speckle, on the transport properties of a Bose-Einstein condensate. Recent proposals in condensed matter to demonstrate a "superinsulator", in which there is a finite temperature transition between a conducting and insulating state in 1D may be realizable using cold atoms. A closely related topic is to understand the role of interactions in Anderson Localization by measuring the localization length as a function of interparticle interaction.Finally, the broad Feshbach resonance enables access to the regime of strong interactions where the mean-field theory of Bose-Einstein condensation breaks down. Both the perturbative regime, where the energy is corrected in powers of many time the cube of the scattering length and the regime of strong condensate depletion are being explored.Wave/particle duality is at the heart of quantum physics. At very low temperatures, we find that particles that ordinarily act as compact solid objects behave as if they are waves, that is, they reflect, diffract, and interfere. Bose-Einstein condensates (BECs) of atoms are iconic examples of such behavior. A BEC is a collection of atoms that become a single quantum mechanical wave at temperatures as low as one millionth of a degree above absolute zero. In this program, we create BECs of interacting lithium atoms and use them to explore and test some of the most fundamental ideas of quantum mechanics, including the tunneling of particles through otherwise impenetrable barriers. These experiments are enabled by the ability to tune the strength of the interatomic interactions and to even change whether they are repulsive or attractive. By making them weakly attractive, the BECs form a soliton, which is a packet of waves that can travel over a distance without dissipating. Under some conditions a BEC soliton may behave as a single "super-atom", thus stretching the realm of quantum mechanics to ever larger objects, much like the famous Schrodinger Cat. We also tune the interactions to the opposite extreme, where the interactions are repulsive and very strong. These BECs are being used to test our theories of strongly interacting matter. These experiments will give us a greater understanding of the quantum realm, which hopefully, will allow us to exploit quantum phenomena, such as superconductivity, for practical applications.

锂原子表现出极其广泛的费什巴赫共振，Li-7 最低超精细亚能级的费什巴赫共振延伸到大约 200 高斯 (G) 的范围，在该范围内它会经历斜率仅为 0.1 ao/G 的零交叉，其中ao 是玻尔半径。我们的工作利用费什巴赫共振的特性来研究具有吸引力、弱或很强相互作用的玻色子。明亮物质波孤子的产生，先前通过弱吸引 Li-7 原子证明，我们通过使孤子在一维光陷阱中在一维光陷阱中执行偶极子振荡来研究基本量子现象。该系统可能会表现出显着的相干复合，从而为明亮物质波孤子干涉仪奠定基础。我们的第二个项目是致力于实现真正的宏观量子隧道效应。这项研究研究了光学散斑产生的无序电势对玻色-爱因斯坦凝聚态输运特性的影响。最近提出的凝聚态物质证明了“超绝缘体”，其中导电体和超绝缘体之间存在有限的温度过渡。一维绝缘态可以使用冷原子来实现，一个密切相关的主题是通过测量作为粒子间相互作用函数的局域长度来理解相互作用在安德森局域化中的作用。费什巴赫共振能够实现玻色-爱因斯坦凝聚的平均场理论的强相互作用状态，其中能量以散射长度的立方的多次幂进行校正的微扰状态和强凝聚状态。波/粒子二象性是量子物理学的核心，我们发现在非常低的温度下，通常充当致密固体的粒子表现得就像波一样，也就是说，它们。原子的玻色-爱因斯坦凝聚体 (BEC) 是这种行为的典型例子，BEC 是在温度低至高于绝对零百万分之一度时变成单个量子机械波的原子集合。在这个项目中，我们创建了锂原子的 BEC，并用它们来探索和测试量子力学的一些最基本的思想，包括粒子穿过其他不可穿透的障碍的隧道，这些实验是通过调谐能力来实现的。原子间相互作用的强度，甚至改变它们是排斥的还是吸引的，通过使它们具有弱吸引力，BEC 形成了一个孤子，它是一组在某些条件下可以传播很远距离而不会消散的波。可能表现为单个“超级原子”，从而将量子力学的领域扩展到更大的物体，就像著名的薛定谔猫一样。我们还将相互作用调整到相反的极端，其中相互作用是排斥的并且非常强。 BEC 被用来测试我们的强相互作用物质理论，这些实验将使我们对量子领域有更深入的了解，这有望使我们能够利用超导等量子现象进行实际应用。