Simulating ultracold quantum chemistry at conical intersections

计算分子的电子结构和动力学是现代量子化学领域的核心挑战。随着计算成本随着分子的大小呈指数级增长，在经典计算机中解决电子结构问题成为一项艰巨的任务。然而，现在量子计算和模拟变得越来越容易理解和解释复杂的多体量子态和分子动力学。使用量子计算机开发的，例如，IBM和谷歌，电子结构在低洼国家已成功确定。尽管如此，仍然存在具有挑战性的任务，其中之一是调查电子动力学时，两个紧密躺在电子势能面在高维坐标空间交叉。这种特殊的点形成了一个圆锥形的交叉点，在那里发生了由拓扑效应和非绝热转变控制的有趣的化学过程。锥形交叉点在许多光化学和光生物学反应中也起着关键作用，如DNA的视觉和稳定性。然而，直接观察所产生的非绝热动力学是困难的，因为它发生在飞秒时间尺度和几埃的长度尺度上。因此，任何测量都会激发分子的大量振动状态，这不可避免地导致加热。这不仅阻碍了量子和拓扑效应的观察，而且在理论上解释实验时也造成了障碍。此外，常用的方法，如玻恩-奥本海默近似，失败附近的圆锥相交。为了应对这一挑战，我们将进行一项研究计划，引入一个模拟量子模拟平台-由一对相互作用的被困里德伯离子组成-来设计锥形交叉点，并分别在纳米和微秒量级的长度和时间尺度上研究它们随后的动态。在离子阱中，离子的振动态可以被激光冷却到接近零的温度，从而可以研究圆锥形交叉点附近的完全相干过程。这为在真实的时间内模拟和探测超冷量子化学铺平了一条新的途径，即在最先进的囚禁离子装置中通过直接光谱测量。在我们最初工作的基础上，该建议的目的也是揭示新的多体非平衡和拓扑现象，这些现象是由圆锥形交叉点实现的，但在分子中没有直接的对应物。这将通过Rydberg离子量子模拟器提供的尺寸，大小，电子振动耦合的前所未有的可控性水平来实现。预期产出不仅对相关学术界，而且对量子技术的持续发展都具有高度相关性。我们将建立一个全面的理论框架，用于模拟量子化学与捕获的里德伯离子，并通过与国际上领先的实验组密切合作，我们将设计协议，以探测相干动力学和效果。我们的跨学科研究将在英国与国际捕获离子和里德伯物理社区之间建立联系，从而加强英国在量子模拟和量子计算领域的世界领先地位。

Computing the electronic structure and dynamics of molecules is a central challenge in the field of modern quantum chemistry. As the computational cost grows exponentially with the size of the molecule, solving the electronic structure problems in a classical computer becomes a formidable task. However, nowadays quantum computation and simulation become increasingly available to understand and characterise intricate many-body quantum states and the dynamics of molecules. Using quantum computers developed at, e.g., IBM and Google, electronic structures in low-lying states have been successfully determined. Nevertheless, challenging tasks remain, with one being the investigation of electronic dynamics when two close-lying electronic potential energy surfaces cross in high dimensional coordinate space. Such exceptional point forms a conical intersection, where intriguing chemical processes governed by topological effects and non-adiabatic transitions occur. Conical intersections also play critical roles in many photochemical and photobiological reactions, such as vision and stability of DNA. However, directly observing the resulting non-adiabatic dynamics is difficult, as it takes place on a femtosecond time scale and on length scales of a few Angstroms. As a result, any measurement will excite a vast number of vibrational states of the molecule, which inevitably leads to heating. This not only prevents the observation of quantum and topological effects, but also causes obstacles in interpreting the experiment theoretically. Furthermore, commonly used approaches, such as the Born-Oppenheimer approximation, fail near conical intersections. In order to address this challenge, we will conduct a research programme that introduces an analogue quantum simulation platform - consisting of a pair of interacting trapped Rydberg ions - to engineer conical intersections and to investigate their ensuing dynamics at length and time scales of the order of nanometres and microseconds, respectively. In an ion trap, the vibrational states of the ions can be laser cooled to nearly zero temperature, allowing the study of fully coherent processes in the vicinity of a conical intersection. This paves a new route towards simulating and probing ultracold quantum chemistry in real time via direct spectroscopic measurements in state-of-the-art trapped ion setup. Building on our initial work, the aim of this proposal is also to uncover novel many-body non-equilibrium and topological phenomena which are enabled by conical intersections but have no immediate counterpart in molecules. This will be enabled by the unprecedented level of controllability over the dimension, size, electron-vibration couplings offered by the Rydberg ion quantum simulator. The expected outputs will be of high relevance not only for the related academic community, but also for the ongoing development of quantum technologies. We will establish a comprehensive theoretical framework for simulating quantum chemistry with trapped Rydberg ions, and by working closely with the internationally pioneering experimental group, we will design protocols to probe coherent dynamics and effects. Our interdisciplinary research will create connections between the UK and the international trapped ion and Rydberg physics communities and thereby strengthen the UK's world-leading position in the area of quantum simulation and quantum computation.