Advisor(s): Yiming Wang

Committee members:

Kay BrummondPaul FloreancigMartin Walker (Chemistry, Potsdam State University of New York)

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Abstract: Superconducting circuits are a leading platform for quantum information processing because of their flexibility as engineered quantum systems. Parametric controls provide an effective and flexible approach for manipulating superconducting circuits. In parametric control, appropriate choices of drive frequency, amplitude, and phase activate nonlinear Hamiltonian terms that turn on selected interactions and control them dynamically. In designing a SNAIL-mediated four-qubit quantum module, this work demonstrates parametrically activated single- and two-qubit control. However, design tradeoffs appear when stronger coupling and faster gates are pursued. To push parametric control further, this thesis uses transmons to explore subharmonic driving, subharmonic measurement, and a general strong-drive limit that applies not only to transmons but also to other superconducting circuits.

Subharmonic single-qubit control is demonstrated using a drive near one third of the qubit transition frequency, where the Josephson nonlinearity converts three drive photons into one excitation of the computational transition. This frequency separation allows the control line to be filtered strongly at the qubit frequency while still passing the lower-frequency control tone. With phase tracking, chirped modulation, transfer-function correction, and leakage-aware pulse tuning, this protocol realizes single-qubit gates with a best fidelity above 99.9% and π and π/2 gate times of 50.9ns and 37.4ns, respectively. I then extend the same idea to measurement by using an alternate subharmonic drive to generate a resonator field through the transmon nonlinearity. The resulting dispersive readout achieved a best measurement fidelity of 95.0%, and the model indicates that improved lifetime, frequency planning, and readout parameters can push the protocol toward much higher fidelity.

The second part of the dissertation studies the strong-drive threshold that limits parametric control. In experiments on strongly driven circuits, the driven mode population spreads into many highly excited transmon levels above a critical drive amplitude, causing the intended coherent response to disappear. I identify this breakdown as a speed limit for parametric interactions. By comparing simulations with experimental characterization, the model successfully predicts this threshold in driven transmons. This threshold model provides a tool for estimating the limits of parametrically driven systems and designing new devices that can further improve parametric control

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Advisor(s): Haitao Liu

Committee members:

Jill MillstoneXin GuiMichael Therien (Department of Chemistry,Duke)

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Abstract: Over the last several decades, significant advances in our understanding of cellular and physiological processes that result in the initiation and progression of malignancy have been achieved. These insights have led to new treatments involving immunotherapy and targeted approaches to combat the cancer process. This presentation will discuss these advancements and take a look back at some of the individuals and their pioneering contributions that laid the foundation for the progress in cancer treatment that has been realized in recent decades. Finally, while the scientific and medical communities continue to pursue cures, the presentation will conclude by discussing how prevention, screening, and early intervention currently offer the best hope for achieving a cure.

Bio: Dr. Lomis is a fellowship trained surgical oncologist with extensive experience in the surgical management of complex cancer cases. He studied at the University of Pittsburgh, receiving a master’s degree in medicinal chemistry in 1987 and medical degree in 1992. He is the CEO and medical director of the San Fernando Valley Cancer Center and Valley Breast Care, with three sites in the Greater Los Angeles area. He conducts scientific research projects related to the development of novel compounds, including radioligand agents, to more precisely target cancer cells. He is the principal investigator for the San Fernando Valley site on several national clinical trials for Translational Research in Oncology-US Network. Current trials involve the evaluation of CDK4/6 inhibitors and antibody drug conjugates, one of which, the NATALEE trial, led to FDA approval of ribociclib for expanded use in the treatment of breast cancer.

Thomas Lomis M.D., M.S.
Surgical Oncologist
Medical Director, San Fernando Valley Cancer Center and Valley Breast Care

See more of Dr. Lomis's research on his website: https://www.researchgate.net/profile/Thomas-Lomis

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Abstract: Characterizing exoplanet atmospheres is essential to understanding the formation pathways and evolutionary processes underlying the diversity of planetary systems we observe today. Although space-based observations have dominated atmospheric characterization, advancements in both instrumentation and data processing techniques have enabled ground-based high-resolution spectroscopy (HRS) to emerge as a powerful tool for probing exoplanetary atmospheres. HRS has the capability to resolve individual exoplanetary spectral lines and detect species present in the atmosphere through cross-correlation, while newly emerging cross-correlation-to-log-likelihood (CC-to-log L) mapping techniques allow for quantitative constraints on the chemistry and thermal structure of gas giant exoplanets. In this thesis, I develop a Bayesian retrieval framework built on CC-to-log L mapping and apply it to emission spectroscopy of the ultra-hot Jupiter (UHJ) KELT-20 b, constraining its chemical composition and pressure-temperature profile and deriving separate dayside and nightside terminator constraints that reveal differences in chemistry and temperature as a function of planetary longitude. Building on this foundation, I introduce further advancements to the retrieval framework that allow for greater flexibility in chemical and pressure-temperature parameterizations, and apply this approach to an emission spectroscopic survey of four UHJs, whose initial results reveal trends in atmospheric chemistry across the sample, including evidence for atmospheric nickel enrichment and a temperature-dependent depletion of calcium and titanium. Finally, I discuss the implications of these findings for the physical and chemical processes that shape ultra-hot Jupiter atmospheres, along with the continuing role of HRS in advancing our understanding of exoplanet formation and evolution.

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Advisor(s): Sean Garrett-Roe

Committee members:

Jennifer LaaserJessica AnnSusan Fullerton (Department of Chemical and Petroleum Engineering, University of Pittsburgh)

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Advisor(s): Jill Millstone

Committee members:

Nathaniel RosiHaitao LiuSara Bals (Department of Physics, University of Antwerp, Belgium)

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Advisor(s): Yiming Wang

Committee members:

Kay BrummondPeng LiuMartin Walker (SUNY Potsdam)

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Advisor(s): Seth Horne

Committee members:

Lillian ChongSeth ChildersJuan Del Valle (University of Notre Dame)

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