Physics 838 Graduate Student Seminar

In 1990, a seminar was initiated for QMC (formerly CNAM/CSR) graduate students in order to present their research to the other students, postdocs, and faculty in the Center. In addition to fostering a rich, collaborative environment in which students learn about the breadth and scope of research being done in QMC, the idea of this series is to teach several crucial skills to our students:

1) How to present their research in a clear and time-efficient way to an audience that was not expert in their area of research;

2) How to best answer questions during their presentations;

3) How to ask good questions when in an audience (or interview), in particular about research beyond their own narrow PhD topic.

In this seminar, students submit formalized feedback to each weekly presenter, providing informative information about presentation style, research content and tips for improvement.

Best Speaker Awards

At the end of each term, a cash prize award is given for the best student and postdoc presentations based on class feedback scores. Previous winners are listed here:

2023 (fall) Jared Erb (student), Peter Czajka (postdoc)

2022 (fall) Sungha Baek (student), Keenan Avers (postdoc)

2020 (fall) Shukai Ma 

2019 (spring) Rui Zhang (student), Tarapada Sarkar (postdoc)

2018 (fall) Chris Eckberg (student), Jen-Hao Yeh (postdoc)

2015 Paul Syers, Jasper Drisko

2014 Sean Fackler, Paul Syers,

2013 Kevin Kirshenbaum, Kirsten Burson

2012 Baladitya Suri, Kristen Burson

2011 (fall) Sergii Pershoguba, Ted Thorbeck

2011 (spring) Anirban Gangopadhyay, Baladitya Suri

2010 (fall) Christian J. Long, Tomasz M. Kott

2010 (spring) Tomasz M. Kott, Kevin Kirshenbaum

2009 (fall) Arun Luykx, Jen-Hao Yeh

PHYS838C Seminar: Kungang Li, UMD

Calendar
Physics 838 Seminar
Date
05.10.2021 4:00 pm - 5:30 pm

Description

Speaker: Kungang Li, UMD

Title: T1 fluctuations in long lived transmons

Abstract: 
We measured the relaxation time T1 of transmons made with thin-film electrodes of pure Al and counter-electrodes made with either pure Al or oxygen-doped Al. The superconducting energy gap of each layer depends on the grain size, which depends on the oxygen doping, and the layer’s thickness. At 20 mK an oxygen-doped device showed T1 variations between about 80 μs and 300 μs, while an un-doped device on the same chip showed uncorrelated T1 variations between about 50 and 100 μs. In these devices, T1 fluctuated on the time scale of minutes, with a standard deviation that was proportional to T1, even above 150 mK, where the relaxation was dominated by thermally-generated quasiparticles. This behavior is not consistent with fluctuations in two-level-system dielectric loss or fluctuations in the density of non-equilibrium quasiparticles. We propose a mechanism that involves fluctuations in quasiparticle dissipation channels and find it yields fluctuations that are consistent with the observed behavior.    



Advisor: Wellstood Lobb

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https://umd.zoom.us/j/96975735470?pwd=V3lPTkdYTHRCTU5UcHlWTThtcEZSdz09

Meeting ID: 969 7573 5470
Passcode: 005596