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

基本信息

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

项目摘要

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.

扔进池塘的鹅卵石向外传播的涟漪是常见的景象。仔细观察发现，每个波纹或波浪在传播时都会扩散，从而降低高度或幅度，直到到达池塘边缘时几乎消失。然而，值得注意的是，存在一种波的形式，它不会扩散或分散，因此可以传播很远的距离而振幅没有任何变化。这种波被称为孤子，1834 年首次被观察到是苏格兰运河上的窄船产生的弓波。如今，孤子出现在许多不同的物理系统中，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找到了重要的应用。所有这些例子的共同点是存在控制系统中波传播的非线性波动方程。现在通常使用激光将碱金属原子的稀释气体冷却到百万分之一绝对零度以内，从而允许它们被限制在陷阱中由于施加的磁场与每个原子的微小磁矩的相互作用而形成。通过蒸发进一步冷却导致产生一种新的物质状态，称为玻色-爱因斯坦凝聚，其中粒子的量子力学性质主导了它们的经典行为。该系统的状态也受非线性波动方程的控制，其中非线性是由原子与原子的相互作用产生的。此外，如果系统中的原子相互作用具有吸引力，那么凝聚态就可以形成明亮的物质波孤子；原子的脉冲或波包，就像运河上的弓波一样，在传播时不会扩散。该提案的目的是研究铷 85 原子凝聚体中此类孤子的形成和动力学。铷 85 原子之间的碰撞会产生散射共振，称为费什巴赫共振，它可以精确控制原子相互作用，这对于系统研究孤子形成至关重要。此外，光学偶极子陷阱的使用允许实时修改限制势，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，明亮物质的产生波孤子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针的长期研究目标的一部分。吸引原子-表面相互作用是量子电动力学中的一个基本问题，具有悠久而重要的理论历史。然而，直到最近才通过实验测量了这种相互作用。最近，超冷原子的高度控制已经催生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，粒子从电势反射而没有达到经典转折点。该提案旨在证明固体表面孤子的量子反射，作为测量原子与表面相互作用的第一步。使用定位良好的孤子，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。此类研究的动机是，由于超出标准模型的外力，原子与表面相互作用的精确测量将来可能会对重力的短程修正设置新的限制。