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Events on Tuesday, October 27th, 2020

PGSC phenomeNal Open Graduate Seminar
Time: 2:30 pm
Speaker: Trevor Oxholm, Physics PhD Graduate Student
Abstract: You're Gonna Go Far, KID: cosmology with superconducting Kinetic Inductance Detectors on balloon- and space-based missions
Sub-millimeter astronomy is entering a new frontier. Earth’s atmosphere plagues ground-based sub-mm telescopes with high levels of background radiation, so astronomers are relocating their instruments to high-altitude balloons, and in the near future, onto satellites. This new era of low-background sub-mm astronomy requires highly sensitive detector technologies, for which we turn to superconductivity. The Kinetic Inductance Detector (KID), a superconducting microresonator technology that has only recently seen its first light, is being commissioned for this new generation of instruments. The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM), led by NASA-Goddard Space Flight Center scientists, is among the first in this class of instruments. I will describe the technology behind KIDs designed for EXCLAIM, and the science we plan to accomplish. I will also describe the potential for the use of KIDs in future space missions, along with the science that can be accomplished with such a low-background, highly sensitive survey of the cosmos.
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Thesis Defense
Circuit Quantum Electrodynamics with Si/SiGe Quantum Dots
Time: 3:00 pm
Speaker: Nathan Holman, Physics PhD Graduate Student
Abstract: In this talk I present an approach to engineering quantum mechanical circuits utilizing superconducting resonators and Si/SiGe quantum dots in a cQED framework as a basis for quantum computing technology. I will discuss the microwave engineering principles for the quantum dot wiring to nearly eliminate unintended resonator photon leakage out the dot leads without the use of on chip lumped element LC filters. Using this approach, quality factors as high as 30k have been achieved and are limited by the intentional coupling of the resonator to the readout lead. Next, I discuss the development and characterization of a novel growth technique for an ultrathin (< 2 nm) and high quality SiO2 gate dielectric aimed at reducing charge noise. As a demonstration of improved charge coherence, I will show low frequency (< 500 MHz) Landau-Zener-Stückelberg-Majorana interferometry experiments of a dressed valley-orbit state. Lastly, I will present ongoing efforts to further improve device performance and reproducibility by decoupling the fabrication of the quantum dots and resonators using a multi-chip module architecture. Preliminary measurements of a double and triple quantum dots coupled to an off chip, high impedance TiN resonator will be shown.
Host: Mark Eriksson, Faculty Advisor
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Council Meeting
Time: 4:00 pm - 5:00 pm
Place: Virtual
Speaker: Sridhara Dasu, UW-Madison
Host: Sridhara Dasu, Department Chair
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