Nonadiabatic Transition Probabilities: Applications in Spectroscopy, Quantum Thermodynamics, and Quantum Computing

在化学系化学理论、模型和计算方法项目的支持下，密歇根州立大学的凯瑟琳·亨特（Katharine Hunt）正在开发新的量子力学理论和计算分析，以确定外部电磁场引起的分子状态变化。亨特和她的研究小组将分析随时间变化的电磁场诱导分子从初始量子态向激发态转变的可能性。该结果有望在分析能量摄取和能量转换装置方面具有重要应用。量子奥托发动机的功、热、功率和效率将在亨特研究小组开发的新理论中进行分析。这一分析有望表明，在将热量转化为有用功方面，量子引擎可以超越传统的卡诺极限。该分析还可能提出提高量子制冷机性能的方法，由于电子元件尺寸的缩小和相关的散热问题，需要改进量子制冷机。亨特研究小组将与实验研究小组合作，对这一理论进行新的测试。该理论将应用于量子计算的背景下，提出可能最大限度地减少误差的新算法，并探测量子纠缠的影响。除了上述对工程和计算机科学的潜在广泛影响外，该项目还将通过将本科生和高中生纳入研究团队以及编写教学文章，在将STEM（科学、技术、工程和数学）研究与教育结合方面产生更广泛的影响。整个项目将鼓励妇女、残疾人和代表性不足的少数民族充分参与。亨特小组探索了一种超越狄拉克跃迁理论的理论，将量子系统的实际激发与对扰动的绝热响应分开。该小组将开发方法来充分考虑激发态的退相干和衰变，从而预测激发态的占用，预计在扰动结束后与狄拉克理论不同。多芳香族化合物的振动光谱、小分子的超快光谱和大分子中的非绝热电子跃迁将被用作测试案例。此外，将研究通过stark诱导的绝热拉曼通道在选定的激发态下产生分子，并将非零相阻尼的潜在影响添加到现有理论中。当应用于量子奥托发动机的操作时，已知亨特群理论在功率冲程结束时的量子态占比与先前的理论产生差异；它有望预测整体发动机效率的差异，超过卡诺极限。本文将研究一种新的绝热量子计算算法，该算法基于非绝热和绝热响应的逐步分离，以减少误差。预计这项工作将通过应用于有限时间量子操作、能量摄取和转换设备、量子引擎、量子冰箱和量子计算，对工程和计算机科学产生更广泛的影响。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。

With support from the Chemical Theory, Models and Computational Methods program in the Division of Chemistry, Katharine Hunt of Michigan State University is developing new quantum mechanical theory and computational analyses to determine the changes in molecular states caused by external electromagnetic fields. Hunt and her research group will analyze the probability for a time-dependent electromagnetic field to induce transitions from the initial quantum state of a molecule to excited states. The results are expected to have important applications in analyzing energy uptake and energy conversion devices. The work, heat, power, and efficiency of quantum Otto engines will be analyzed within the new theory developed by the Hunt research group. This analysis is expected to show that quantum engines can exceed traditional Carnot limits on the conversion of heat into useful work. The analysis may also suggest means of improving the performance of quantum refrigerators, which are needed due to the push to reduce the size of electronic components and the associated problems of heat dissipation. Novel tests of the theory will be carried out in collaborations by the Hunt research group with experimental research groups. The theory will be applied in the context of quantum computing, to suggest new algorithms that may minimize error and to probe effects of quantum entanglement. In addition to the potential broader impacts in engineering and computer science mentioned above, the project will have broader impact in integrating STEM (science, technology, engineering and mathematics) research with education, through the inclusion of undergraduates and high school students in the research team and the preparation of pedagogical articles. The full participation of women, persons with disabilities, and underrepresented minorities will be encouraged throughout the project.The Hunt group has explored a theory that goes beyond Dirac’s theory of transitions, to separate the actual excitations of quantum systems from the adiabatic response to a perturbation. The group will develop methods to take full account of decoherence and decay of excited states, leading to predictions for the occupancy of excited states that are expected to differ from Dirac theory, after a perturbation has ended. Vibrational spectroscopy of polyaromatic compounds, ultrafast spectroscopy of small molecules, and nonadiabatic electronic transitions in larger molecules will be used as test cases. In addition, the production of molecules in selected excited rovibrational states via Stark-induced adiabatic Raman passage will be investigated, with the potential effects of non-zero phase damping added to the existing theory. As applied to the operation of quantum Otto engines, the Hunt-group theory is known to produce differences from previous theories in the quantum-state occupancies at the end of the power stroke; it is expected to predict differences in the overall engine efficiency, surpassing the Carnot limits. A new algorithm for adiabatic quantum computing will be investigated, based on step-wise separation of nonadiabatic and adiabatic response, to reduce errors. The work is expected to have broader impact in engineering and computer science, through applications to finite-time quantum operations, energy uptake and conversion devices, quantum engines, quantum refrigerators, and quantum computing.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.