Graduate Program Events

<< Summer 2023 Fall 2023 Spring 2024 >>
Subscribe your calendar or receive email announcements of events

Events on Thursday, November 9th, 2023

Generation and detection of axions using four-wave mixing in optical fibers
Time: 9:00 am - 11:00 am
Place: 5280 Chamberlin
Speaker: Shay Inbar, Department of Physics Graduate Student
Abstract: The axion is a hypothetical particle originally postulated to solve the strong CP problem in particle physics. It is also a promising candidate to be dark matter, which had been a long-standing problem in physics and cosmology: the evidence for its existence is abundant, yet no direct measurement has confirmed it as of yet, and its nature is unknown. The speculated role of the axion in both these puzzles had motivated experimental searches for it. We propose an experimental scheme for the generation and detection of axions using four-wave mixing in optical fibers. Advantages of this scheme are the large interaction length inside the optical fibers, and our control of the operating lasers, which allows for the scanning of a range of axion masses.
Add this event to your calendar
Preliminary Exam
Extracting Contributions to Qubit Loss from Superconducting Microwave Resonators
Time: 10:30 am - 12:00 pm
Place: 2104 Chamberlin
Speaker: Shravan Patel, Department of Physics Graduate Student
Abstract: Superconducting coplanar waveguide resonators play a critical role in information storage and qubit state measurement in superconducting quantum information processing. At the same time, these resonators are a versatile testbed for characterizing the various contributions to qubit loss. Ideally, the internal quality factors Qi of these resonators should reach ten million or higher, limited only by the loss tangent of the silicon or sapphire substrate. However, in real devices, Qi is limited by the presence of various loss channels, including two-level state (TLS) defects at amorphous interfaces, trapped magnetic flux vortices, and nonequilibrium quasiparticles. In this work, we measure Qi as a function of photon occupation in Al and Nb thin-film microwave resonators with different center conductor and gap widths. This allows us to extract the contribution to loss from interfacial TLS defects. We have also implemented novel resonator designs, including tapered resonators to study the relative contributions to loss from TLS and quasiparticles. We have characterized devices fabricated on different substrates, used several methods to deposit the Al and Nb films, and explored surface cleaning techniques to remove the native silicon oxide immediately prior to cooling the resonators.
Add this event to your calendar