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

点击翻译按钮获取中文摘要

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.