Ultracold Triatomic Molecules

原子和分子是世界的微观组成部分。它们的行为和相互作用受量子力学理论的支配，量子力学在基本层面上描述了现代科学和技术的大部分。然而，在第二次量子革命中推进量子科学和技术需要冷却到绝对零度以上百万分之一度左右的温度。在过去的几十年里，强大的激光冷却技术已经发展到用原子达到这些“超冷”温度;反过来，许多发现揭示了复杂系统中量子物理的复杂性，并导致了有用的量子计算机的创建。这些技术最近已经扩展到双原子分子（包含两个原子），但更大的分子（“多原子”）迄今为止还没有完全的量子控制。冷却多原子分子将揭示化学反应的量子本质，并成为更强大的量子模拟的资源，这可能导致新技术材料的开发。在这个项目中，John Doyle教授和他的研究生、本科生和博士后研究人员将使用激光冷却在超冷温度下捕获CaOH（氢氧化钙）分子，然后研究它们的碰撞，这将揭示分子相互作用背后的量子物理学。我们的目标是最终建立一个量子计算机使用单分子阵列的CaOH分子。这项工作的实验起点将是冷却和捕获CaOH分子在磁光阱（MOT）。这将需要从分子中散射数万个可见光子以去除能量和动量，这是通过仔细理解Doyle教授及其研究小组最近开发的CaOH的振动结构实现的。因为像CaOH这样的多原子分子不能无限期地散射光子，它们将被转移到一个保守的光偶极阱（ODT）中，在那里它们可以保持几秒钟而不会丢失。在那里，它们也可以被亚多普勒冷却到接近1μK的温度。通过将大约104个分子加载到ODT中，应获得足够的密度以研究CaOH分子之间的碰撞。在使分子处于激发振动状态并施加约1 kV/cm的适度DC电场后，预计非弹性碰撞将被有效屏蔽，从而使三原子分子蒸发冷却至甚至更低的温度。研究人员还提出将CaOH分子装入光镊中，这为碰撞研究提供了另一种途径，也可用于实施新的量子模拟和计算方案。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Atoms and molecules are the microscopic building blocks of the world. Their behavior and interactions are governed by the theory of quantum mechanics, which describes at a fundamental level much of modern science and technology. However, advancing quantum science and technology in the second quantum revolution requires cooling to temperatures around one millionth of a degree above absolute zero. Over the past several decades, powerful laser cooling techniques have been developed to reach these “ultracold” temperatures with atoms; in turn, a number of discoveries were made that shed light on the intricacies of quantum physics in complicated systems and led to the creation of a useful quantum computer. These techniques have more recently been extended to diatomic molecules (containing two atoms), but larger molecules (“polyatomic”) have so far eluded full quantum control. Cooling polyatomic molecules will shed light on the quantum nature of chemical reactions and be a resource for yet even more powerful quantum simulation, which can lead to the development of new technological materials. In this project, Professor John Doyle and his research team of graduate and undergraduate students and postdoctoral researchers will use laser cooling to trap CaOH (calcium monohydroxide) molecules at ultracold temperatures and then study their collisions, which will shed light on the quantum physics underlying molecular interactions. The aim is to eventually build a quantum computer using single molecule arrays of CaOH molecules.The experimental starting point of this work will be to cool and trap CaOH molecules in a magneto-optical trap (MOT). This will require scattering tens of thousands of optical photons from the molecules to remove energy and momentum, which is enabled by a careful understanding of the vibrational structure of CaOH developed recently by Professor Doyle and his research group. Because polyatomic molecules like CaOH cannot scatter photons indefinitely, they will then be transferred into a conservative optical dipole trap (ODT) -- where they can be held for several seconds without being lost. There, they can also be sub-Doppler cooled to temperatures near 1μK. By loading approximately 104 molecules into the ODT, sufficient density should be obtained to study collisions between CaOH molecules. After populating the molecules in an excited vibrational state and applying modest DC electric fields of ~1 kV/cm, it is expected that inelastic collisions will be effectively shielded, enabling evaporative cooling of triatomic molecules to even lower temperatures. The researchers additionally propose to load CaOH molecules into optical tweezers, which present an alternative route to collisional studies and could also be used to implement novel quantum simulation and computation schemes.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.