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

在化学系化学理论、模型和计算方法计划的支持下，密歇根州立大学的凯瑟琳·亨特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态的变化。亨特和她的研究小组将分析依赖于时间的电磁场诱导从分子的初始量子状态到激发状态转变的可能性。这一结果有望在分析能量吸收和能量转换装置方面有重要的应用。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，量子引擎可以超过传统的卡诺限制，将热量转化为有用的功。这项分析还可能提出改进量子制冷机性能的方法，这是由于推动缩小电子元件的尺寸以及相关的散热问题而需要的。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，以提出可能将误差降至最低的新算法，并探索量子纠缠的影响。除了上述对工程和计算机科学可能产生的更广泛的影响外，该项目还将通过吸收本科生和高中生加入研究小组和编写教学文章，在将STEM(科学、技术、工程和数学)研究与教育相结合方面产生更广泛的影响。在整个项目中，将鼓励妇女、残疾人和少数族裔的充分参与。亨特团队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微扰的绝热反应分开。该小组将开发方法，充分考虑激发态的退相干和衰变，从而预测在微扰结束后，激发态的占有率预计将不同于狄拉克理论。多芳化合物的振动光谱、小分子的超快光谱以及大分子的非绝热电子跃迁将被用作测试案例。此外，还将研究通过斯塔克诱导的绝热拉曼通道产生处于选定激发振荡态的分子，并在现有理论的基础上增加非零位相损耗的潜在影响。由于应用于量子奥托发动机的操作，众所周知，亨特群理论在功率冲程结束时的量子态占有率方面与以前的理论不同；它有望预测整体发动机效率的差异，超过卡诺极限。研究了一种新的绝热量子计算算法，该算法基于非绝热响应和绝热响应的逐步分离，以减少误差。这项工作预计将在工程和计算机科学中产生更广泛的影响，通过应用于有限时间量子操作、能量吸收和转换设备、量子引擎、量子冰箱和量子计算。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.