Bright matter-wave solitons: formation, dynamics and quantum reflection

明亮的物质波孤子：形成、动力学和量子反射

• 批准号: EP/F002068/1
• 负责人: Simon Cornish
• 金额: $ 71.74万
• 依托单位: Durham University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FF002068%2F1
• 关键词: Bright; matter; wave; solitons; formation

The ripples that travel outwards from a pebble dropped in a pond are a familiar sight. Closer inspection reveals that each ripple or wave spreads out as it travels and in so doing decreases in height or amplitude until it has all but vanished by the time it reaches the edge of the pond. Remarkably, however, there exists a form of wave that does not spread out or disperse and which can therefore travel great distances without any change in amplitude. Such waves are known as solitons and were first observed as bow-waves produced by narrow boats on a canal in Scotland in 1834. Today solitons are seen in many different physical systems ranging from waves in plasmas to optical pulse propagation in nonlinear media. The latter example now finds important applications in long distance optical fibre communication systems. Common to all these examples is the existence of a nonlinear wave equation governing wave propagation in the system.Dilute gases of alkali atoms are now routinely cooled to within a millionth of a degree of absolute zero using laser light, permitting them to be confined in traps formed due to the interaction of an applied magnetic field with the minute magnetic moment of each atom. Further cooling by evaporation leads to the creation of a new state of matter, known as a Bose-Einstein condensate, in which the quantum mechanical nature of the particles dominates over their classical behaviour. The state of this system is also governed by a nonlinear wave equation in which the nonlinearity results from the atom-atom interactions. Moreover, if the atomic interactions in the system are attractive then the condensate can form a bright matter-wave soliton; a pulse or wave-packet of atoms which, just as for the bow-wave on the canal, does not spread out as it propagates. The objective of this proposal is to investigate the formation and dynamics of such solitons in condensates of rubidium-85 atoms. Collisions between rubidium-85 atoms exhibit a scattering resonance, known as a Feshbach resonance, which permits the precise control of the atomic interactions essential for a systematic investigation of soliton formation. Moreover, the use of optical dipole traps permits the real-time modification of the confinement potential and enables the manipulation of the position and velocity of the solitons for precise collision studies.Just as solitons have found applications in everyday life, the creation of bright matter-wave solitons offers potential future applications in atom interferometry and atom optics. This proposal will assess the feasibility of using matter-wave solitons to investigate the interaction between an atom and a solid surface, as part of the longer-term research goal to construct a tunable matter-wave surface probe . The attractive atom-surface interaction is a fundamental problem in QED and has a long and important theoretical history. It is only relatively recently, however, that this interaction has been measured experimentally. More recently, the high degree of control with which ultracold atoms can be manipulated has lead to several new experimental approaches to probe this interaction. Intimately connected to the measurement of atom-surface interactions is the phenomenon of quantum reflection, whereby a particle is reflected from a potential without reaching a classical turning point as a result of the wave nature of the particle. This proposal aims to demonstrate the quantum reflection of solitons from a solid surface, as a first step towards measuring the atom-surface interaction. The use of well-localized solitons, coupled to the precise control of their velocity, has the potential to take the study of atom-surface interactions to a new level. Such studies are motivated by the possibility that precision measurements of atom-surface interactions may, in the future, set new limits on short range corrections to gravity due to exotic forces beyond the Standard model.

在池塘里扔一块鹅卵石，激起的涟漪是一个熟悉的景象。仔细观察就会发现，每一个波纹或波浪在传播过程中都在扩散，在传播过程中，高度或振幅会降低，直到到达池塘边缘时几乎完全消失。然而，值得注意的是，存在一种不扩散或不分散的波，因此它可以在不改变振幅的情况下传播很远的距离。这种波被称为孤子波，1834年在苏格兰的一条运河上，人们首次观察到这种波是由窄船产生的弓形波。今天，在许多不同的物理系统中都可以看到孤子，从等离子体中的波到非线性介质中的光脉冲传播。后一个例子现在在长距离光纤通信系统中有重要的应用。所有这些例子的共同点是存在一个非线性波动方程来控制波在系统中的传播。现在，用激光将碱原子的稀释气体常规地冷却到绝对零度的百万分之一以内，使它们被限制在由于外加磁场与每个原子的微小磁矩相互作用而形成的陷阱中。通过蒸发进一步冷却会产生一种新的物质状态，称为玻色-爱因斯坦凝聚，在这种状态下，粒子的量子力学性质支配着它们的经典行为。该系统的状态也由非线性波动方程控制，其中非线性是由原子-原子相互作用引起的。此外，如果系统中的原子相互作用是吸引的，则凝聚体可以形成明亮的物质波孤子；一种由原子组成的脉冲或波包，就像运河上的弓形波一样，在传播时不会散开。本文的目的是研究铷-85原子凝聚体中这种孤子的形成和动力学。铷-85原子之间的碰撞表现出散射共振，称为费什巴赫共振，它允许精确控制原子相互作用，这是系统研究孤子形成所必需的。此外，光学偶极子阱的使用允许实时修改约束势，并能够操纵孤子的位置和速度，以进行精确的碰撞研究。正如孤子在日常生活中的应用一样，明亮物质波孤子的创造为原子干涉测量和原子光学提供了潜在的未来应用。该提案将评估使用物质波孤子来研究原子与固体表面之间相互作用的可行性，作为构建可调谐物质波表面探测器的长期研究目标的一部分。吸引原子-表面相互作用是QED中的一个基本问题，有着悠久而重要的理论历史。然而，直到最近，这种相互作用才被实验测量出来。最近，对超冷原子的高度控制导致了几种新的实验方法来探测这种相互作用。与原子表面相互作用的测量密切相关的是量子反射现象，即由于粒子的波动性质，粒子从势反射而没有达到经典的转折点。这个提议的目的是证明从固体表面的孤子的量子反射，作为测量原子-表面相互作用的第一步。良好定域孤子的使用，加上对其速度的精确控制，有可能将原子表面相互作用的研究提升到一个新的水平。这类研究的动机是这样一种可能性：在未来，对原子表面相互作用的精确测量，可能会对标准模型之外的外来力对引力的短距离修正设定新的限制。

项目成果

Magnetic transport apparatus for the production of ultracold atomic gases in the vicinity of a dielectric surface

用于在介电表面附近产生超冷原子气体的磁传输装置

• DOI: 10.48550/arxiv.1109.5340
• 发表时间: 2011
• 作者: Haendel S

Magnetic merging of ultracold atomic gases of $^{85}$Rb and $^{87}$Rb

$^{85}$Rb 和 $^{87}$Rb 超冷原子气体的磁合并

• DOI: 10.48550/arxiv.1011.6273
• 发表时间: 2010
• 作者: Händel S

Generating mesoscopic Bell states via collisions of distinguishable quantum bright solitons.

• DOI: 10.1103/physrevlett.111.100406
• 发表时间: 2013-01
• 期刊: Physical review letters
• 影响因子: 8.6
• 作者: B. Gertjerenken;T. Billam;Caroline L. Blackley;C. Ruth;Le Sueur;L. Khaykovich;S. Cornish;C. Weiss