Quantum Control of Single Polyatomic Molecules

我们周围的分子通常具有数百万种不同的量子态——例如，空气中的单个分子在许多不同的方向上运动和旋转。为了利用这些分子的量子特性，人们需要学习如何在单个量子态中制备单个分子，并测量它们处于哪个状态。这就需要对分子的运动和旋转进行绝对控制。今天，物理学家可以制备单量子态的原子，并以高保真度测量它们所处的状态。这种能力支撑了原子物理学的许多最新进展。制备和测量分子状态的能力远远落后，而且没有一个包含两个以上原子的分子在单一量子态中被制备出来。该项目由物理部原子、分子和光学物理项目以及化学部化学结构、动力学和机制a项目资助，为实现这一目标开发工具。这项工作的一个重要应用是，它可以在不破坏单个分子的情况下识别它们，包括识别这些分子的手性。手性是左手性分子和右手性分子之间的细微差别，它对分子的功能起着重要作用，例如在药物中。这项工作将由加州大学圣巴巴拉分校（UCSB）的研究生和本科生完成，包括参加UCSB EUREKA项目的经济困难学生。该项目将使这些学生获得宝贵的、实际操作的科学技能，同时获得允许他们留在学校的津贴。领导这项研究的科学家们提出了一套方法，使他们能够在单量子态水平上控制大范围的分子离子。本提案的核心是一种新的状态读出方法——量子热测定法，它利用这些分子丰富的内部水平结构来提供单个分子的高保真量子状态读出。单个分子离子将与单个激光冷却的锶离子一起被捕获在混合保罗阱/光学晶格中。分子离子的运动将通过状态依赖的光学晶格和分子内的旋转跃迁的组合来驱动，这些跃迁直接由微波频率电场驱动。与相关的量子逻辑光谱方法相比，该方法不需要边带分辨率或基态冷却。量子热测定法可以应用于大多数较小的（4 - 15个原子）、非球形多原子离子。这些方法将首次允许对单个分子的异构体和对映体进行无损测量，并且允许光谱的分辨率明显高于现有的集合分子光谱技术。这个水平的光谱学将代表我们对分子结构最准确的测定。该奖项反映了美国国家科学基金会的法定使命，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。

The molecules which surround us typically occupy millions of distinct quantum states - for example, individual molecules in the air are moving and spinning in many different directions. In order to take advantage of the quantum properties of these molecules, one needs to learn how to prepare individual molecules in a single quantum state, and to measure which state they are in. This will require absolute control over the movement and rotation of the molecule. Today, physicists can prepare atoms in single quantum states, and measure which state they are in with high fidelity. This ability underpins many of the recent advances in atomic physics. The ability to prepare and measure the state of molecules lags far behind, and no molecule containing more than two atoms has ever been prepared in a single quantum state. This project, funded by the Atomic, Molecular and Optical Physics Program of the Division of Physics, and the Chemical Structure, Dynamics and Mechanisms-A Program of the Division of Chemistry, develops the tools for this goal. An important application of this work is that it will enable the identification of individual molecules without destroying them, including identifying the chirality of these molecules. Chirality is the subtle difference between left-handed or right-handed molecules that can play a big role in how the molecule functions, for example in pharmaceuticals. This work will be done by graduate and undergraduate students at the University of California Santa Barbara (UCSB), including financially disadvantaged students enrolled in UCSB's EUREKA program. The program will allow these students to gain valuable, hands-on scientific skills while earning stipends that allow them to stay in school.The scientists leading this research have proposed a set of methods that will allow them to control a broad range of molecular ions at the single quantum state level. The centerpiece of this proposal is a new state readout method, quantum bolometry, which leverages the rich internal level structure of these molecules to provide high-fidelity quantum state readout of individual molecules. A single molecular ion will be trapped in a hybrid Paul trap/optical lattice, along with a single laser-cooled strontium ion. The molecular ion's motion will be driven via a combination of a state-dependent optical lattice and rotational transitions within the molecule which are driven directly via microwave-frequency electric fields. The method does not require sideband resolution or ground state cooling, in contrast to related quantum logic spectroscopy methods. Quantum bolometry can be applied to most reasonably small (4 - 15 atoms), nonspherical polyatomic ions. These methods will allow for non-destructive measurement of the isomer and enantiomer of individual molecules for the first time, and allow for spectroscopy with a resolution significantly greater than existing ensemble molecular spectroscopy techniques. Spectroscopy at this level would represent our most accurate determination of molecular structure.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.