Cooling molecules to quantum degeneracy

将分子冷却至量子简并

基本信息

批准号：
EP/V011499/1
负责人：
Michael Tarbutt
金额：
$ 186.41万
依托单位：
Imperial College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2021
资助国家：
英国
起止时间：
2021 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FV011499%2F1
关键词：
Cooling molecules quantum degeneracy

项目摘要

Everyone is familiar with the three normal states of matter - solids, liquids and gases. There is also another state, known as a Bose-Einstein condensate (BEC), which is a state of matter that can be described only by quantum mechanics. Due to the uncertainty relation between position and speed, an atom spreads out when it slows down. If a gas of atoms is cooled to very low temperature, the atoms may spread out so much that they all overlap. At this point they coordinate, all gathering together into the quantum state that has the lowest energy, and behaving as a single entity instead of a collection of individuals. This state of matter was predicted in 1924 by Bose and Einstein, and in 1995 researchers created it for the first time by cooling a gas of atoms to less than a microkelvin (a millionth of a degree above absolute zero). Bose-Einstein condensation underlies some extraordinary phenomena such as superfluidity and superconductivity.The study of BECs of atoms has been an immensely fruitful research topic for the last 25 years, and there are strong motivations to extend this to molecules. Importantly, molecules can be polar, having a positive end and a negative end. Due to these electric dipoles, molecules can interact with one another far more strongly than atoms and over much larger distances. In fact, in a BEC of polar molecules, every molecule interacts with every other molecule, creating a strongly interacting quantum system. From these interacting systems emerge new and remarkable phenomena that could not be predicted from the behaviour of the constituents and are far too complex to simulate on a normal computer. Examples include magnetism and high-temperature superconductivity. A molecular BEC would be an ideal, highly controllable system for studying these interacting quantum systems. It may also contribute to the development of quantum computers and improve our understanding of collisions and chemistry at low temperatures. Finally, such low temperatures would hugely improve the precision of ongoing experiments that use molecules to test fundamental physics, such as measurements that search for the origins of matter-antimatter asymmetry.Despite all this motivation, molecules have not yet been cooled to the low temperatures needed for BEC. We aim to do that in this project. We will first use laser cooling, which is a method we have pioneered for molecules over the last few years. Then we will trap the molecules and use collisions to cool them further. Here, there are two approaches. In the first - evaporative cooling - the highest-energy molecules are removed from the trap and the remaining molecules collide and re-distribute the reduced energy, thereby cooling to lower temperatures. In the second - sympathetic cooling - the molecules cool as they collide with atoms at lower temperature. In addition to these crucial temperature-lowering collisions, there can also be bad collisions that cause molecules to change their state, react, or be ejected from the trap. The key to success is to control these collisions, enhancing the good ones and suppressing the bad ones. Our combination of theoretical and experimental expertise will be our guide. The BEC we produce will be a completely new type of quantum matter, whose nature is governed by the strong, long-range dipole-dipole interactions. We will study its behaviour and learn how to control it using electric and magnetic fields, opening up a rich new field of strongly-interacting dipolar matter.

每个人都熟悉物质的三种正常状态——固体、液体和气体。还有另一种状态，称为玻色-爱因斯坦凝聚体（BEC），这是一种只能用量子力学描述的物质状态。由于位置和速度之间的不确定关系，原子在减速时会扩散。如果原子气体被冷却到非常低的温度，原子可能会扩散得太多以致于它们全部重叠。此时，它们进行协调，全部聚集到具有最低能量的量子态，并且表现为单个实体而不是个体的集合。玻色和爱因斯坦于 1924 年预测了这种物质状态，并于 1995 年通过将原子气体冷却到低于微开尔文（绝对零以上的百万分之一度），首次创造了这种物质状态。玻色-爱因斯坦凝聚是超流性和超导性等一些非凡现象的基础。在过去 25 年里，原子 BEC 的研究一直是一个硕果累累的研究课题，并且有强烈的动机将其扩展到分子。重要的是，分子可以是极性的，具有正极和负极。由于这些电偶极子，分子之间的相互作用比原子更强烈，并且距离也更远。事实上，在极性分子的 BEC 中，每个分子都与其他分子相互作用，形成一个强相互作用的量子系统。从这些相互作用的系统中会出现新的、显着的现象，这些现象无法从成分的行为中预测出来，而且过于复杂，无法在普通计算机上进行模拟。例子包括磁性和高温超导性。分子 BEC 将是研究这些相互作用的量子系统的理想的、高度可控的系统。它还可能有助于量子计算机的发展，并提高我们对低温下碰撞和化学的理解。最后，如此低的温度将极大地提高正在进行的使用分子测试基础物理的实验的精度，例如寻找物质-反物质不对称性起源的测量。尽管有这些动机，分子还没有被冷却到低温BEC 需要。我们的目标是在这个项目中做到这一点。我们将首先使用激光冷却，这是我们在过去几年中首创的分子冷却方法。然后我们将捕获分子并利用碰撞进一步冷却它们。这里有两种方法。在第一个过程中 - 蒸发冷却 - 最高能量的分子从陷阱中去除，剩余的分子碰撞并重新分配减少的能量，从而冷却到较低的温度。在第二种情况下——交感冷却——分子在与较低温度的原子碰撞时冷却。除了这些关键的降低温度的碰撞之外，还可能存在导致分子改变状态、发生反应或从陷阱中弹出的不良碰撞。成功的关键是控制这些冲突，增强好的冲突，抑制坏的冲突。我们的理论和实验专业知识的结合将成为我们的指南。我们生产的 BEC 将是一种全新类型的量子物质，其性质由强的长程偶极子-偶极子相互作用决定。我们将研究它的行为并学习如何使用电场和磁场控制它，开辟一个丰富的强相互作用偶极物质新领域。