A Quantum Gas of Ultracold Polar Molecules

超冷极性分子的量子气体

基本信息

批准号：
EP/H003363/1
负责人：
Simon Cornish
金额：
$ 138.96万
依托单位：
Durham University
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FH003363%2F1
关键词：
Quantum Gas Ultracold Polar Molecules

项目摘要

The advent of laser cooling revolutionized atomic physics and precipitated the realization of quantum degenerate gases in which the quantum mechanical nature of the particles dominates over their classical behaviour. These dilute atomic gases, in the form of Bose-Einstein condensates (BEC) and Fermi-degenerate gases, have proved surprisingly rich and are now routinely studied throughout the world. More recently, the quest for the creation of ultracold and quantum degenerate molecular samples has become of paramount interest to both the atomic and molecular physics and physical chemistry communities. The rich internal structure of molecules coupled with the remarkable control afforded by ultracold systems offers enormous scope for applications in fields ranging from precision measurement and high-resolution spectroscopy to ultracold chemistry and quantum information processing. Perhaps most intriguing of all is the possibility to produce ultracold quantum gases of heteronuclear molecules where the long-range, anisotropic dipole-dipole interaction is predicted to give rise to a rich spectrum of novel quantum phases.The laser cooling techniques at the heart of the spectacular experimental advances in atomic physics do not, however, work for molecules due to their complex internal rotational and vibrational structure. This has prompted a host of alternative approaches to create ultracold molecular gases to be developed which all rely on cooling pre-existing molecules from room temperature. This proposal, however, follows an alternative scheme which exploits the huge advances in laser cooling and trapping of atomic gases by carefully assembling ultracold molecules from ultracold atoms. Starting from an ultracold mixed species quantum gas of Rb and Cs, the objective is to create ultracold RbCs molecules in the rovibrational ground state following a two-step conversion process.The first step relies upon the existence of scattering resonances in the collisions between ultracold atoms that result from a coupling between the free atoms and a quasibound molecular state known as a Feshbach resonance. The simple application of an appropriate magnetic field ramp in the vicinity of a Feshbach resonance results in the highly efficient conversion of atoms to molecules whilst preserving the phase-space density of the original atomic sample. However, such Feshbach molecules are extremely fragile; existing in very weakly bound states close to the dissociation threshold they are generally unstable when colliding with each other. The challenge of the second step is to transfer these molecules to the collisionally stable ground state without heating the sample. This can be achieved using a process known as stimulated Raman adiabatic passage (STIRAP) in which two laser fields are applied to the molecule connecting the initial weakly bound state to the ground state via a third excited state. Remarkably, with the appropriate time-dependent laser pulses, the STIRAP process permits the coherent transfer of the molecules to the ground state without populating the excited state thereby removing the possibility of loss due to spontaneous decay. The overall conversion process can be highly efficient with negligible heating so that the temperature and density of the resulting molecular quantum gas mirror the initial parameters of the atomic mixture.In the case of RbCs, it is predicted that rovibrational ground state molecules can be produced using a single STIRAP stage, creating a stable bosonic molecular dipolar quantum gas which could be trapped and further cooled to quantum degeneracy. To achieve this ambitious objective we propose to combine state-of-the-art experiments in synergy with world leading theoretical support into a transformative program of research that stands to cement the UK's position at the forefront of an exciting international field.

激光冷却的出现彻底改变了原子物理学，并促进了量子简并气体的实现，其中粒子的量子力学性质主导了它们的经典行为。这些稀原子气体，以玻色-爱因斯坦凝聚态（BEC）和费米简并气体的形式存在，已被证明含量丰富得惊人，现在全世界都在进行例行研究。最近，对创造超冷和量子简并分子样品的探索已成为原子和分子物理学以及物理化学界的首要兴趣。分子丰富的内部结构加上超冷系统提供的卓越控制能力，为从精密测量和高分辨率光谱到超冷化学和量子信息处理等领域的应用提供了巨大的空间。也许最有趣的是产生异核分子超冷量子气体的可能性，其中长程、各向异性偶极子-偶极子相互作用预计会产生丰富的新型量子相谱。然而，由于分子内部旋转和振动结构复杂，原子物理学中令人瞩目的实验进展并不适用于分子。这促使人们开发出许多替代方法来制造超冷分子气体，这些方法都依赖于从室温冷却预先存在的分子。然而，该提议遵循另一种方案，该方案通过从超冷原子仔细组装超冷分子，利用激光冷却和捕获原子气体方面的巨大进步。从 Rb 和 Cs 的超冷混合物质量子气体开始，目标是通过两步转换过程在振动基态下产生超冷 RbCs 分子。第一步依赖于超冷原子之间碰撞中散射共振的存在这是由自由原子和称为费什巴赫共振的准束缚分子态之间的耦合产生的。在费什巴赫共振附近简单地应用适当的磁场斜坡可以实现原子到分子的高效转化，同时保留原始原子样品的相空间密度。然而，这种 Feshbach 分子极其脆弱；它们以接近解离阈值的非常弱的束缚态存在，当彼此碰撞时它们通常不稳定。第二步的挑战是在不加热样品的情况下将这些分子转移到碰撞稳定的基态。这可以通过一种称为受激拉曼绝热通道（STIRAP）的过程来实现，其中两个激光场被施加到分子上，通过第三个激发态将初始弱结合态连接到基态。值得注意的是，利用适当的时间相关激光脉冲，STIRAP 过程允许分子相干转移到基态，而不填充激发态，从而消除了由于自发衰变而损失的可能性。整个转换过程可以非常高效，加热可以忽略不计，因此所得分子量子气体的温度和密度反映了原子混合物的初始参数。就 RbC 而言，预计可以使用以下方法产生振动基态分子：单个 STIRAP 阶段，产生稳定的玻色子分子偶极量子气体，可以捕获并进一步冷却至量子简并。为了实现这一雄心勃勃的目标，我们建议将最先进的实验与世界领先的理论支持相结合，形成一项变革性的研究计划，以巩固英国在令人兴奋的国际领域的前沿地位。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Feshbach resonances, weakly bound molecular states, and coupled-channel potentials for cesium at high magnetic fields

高磁场下铯的费什巴赫共振、弱束缚分子态和耦合通道电势

DOI：
10.1103/physreva.87.032517
发表时间：
2012-12-21
期刊：
Physical Review A
影响因子：
2.9
作者：
M. Berninger;A. Zenesini;Bo Huang;Walter Harm;H. Nagerl;F. Ferlaino;R. Grimm;P. Julienne;J. Hutson
通讯作者：
J. Hutson

Feshbach resonances in ultracold 85 Rb

超冷 85 Rb 中的费什巴赫共振