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:

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: Ray Mencia, UMD & Calvin He, UMD

Physics 838 Seminar
11.30.2020 4:00 pm - 5:30 pm


Speaker 1: Ray Mencia, UMD

Advisor: Manucharyan  

Title: Ultrahigh-impedance Josephson circuits for quantum computing, simulations, and metrology

Abstract: Chains of Josephson junctions have probably the largest kinetic per-unit-length inductance, which can exceed the geometric one by about 10^4, primarily limited by quantum phase-slip fluctuations. However, the total inductance is also limited by the stray capacitance, which grows linearly with the chain length. This stray capacitance is unnecessarily large in most circuits because of the high dielectric constant of silicon or sapphire substrates. By releasing Josephson chains off the substrate, we can combine the maximal per-unit-length inductance with the minimal stray capacitance, thereby obtaining the highest impedance electromagnetic structures available today. As a first demonstration, we created a superconducting quasicharge qubit (blochnium), a dual of transmon, made of a weak junction shunted by such a large inductance (hyperinductance) that its impedance reaches over 30 × RQ (200 kOhms). In the second demonstration, we fabricated suspended "telegraph" transmission lines, composed of 5,000+ junctions, whose wave impedance exceeds 5 × RQ (32.5 kOhm). These lines are a unique resource in exploring DC current metrology via Bloch oscillations, as well as in analog quantum simulations of many strongly-correlated 1D systems.

Speaker 2: Calvin He

Title:  Relativistic Thomson Scattering as a Potential Intensity Gauge for Petawatt Class Lasers


As new high peak-power pulsed lasers systems are being built around the world, where the most powerful lasers reach above 1 petawatt (PW), new opportunities to explore physics arise along with challenges to measure the intense beams.  The technology to measure the pulsed beam, however, rely on indirect methods that may not accurately represent the full powered beam at the focus.  In this talk, we explore the possibility of a method to directly characterize the laser’s peak intensity at the focus, name by measuring radiation from electrons scattered at the laser focus, also known as Relativistic Thomson Scattering (RTS).  We present a proof-of-principal study where the onset wavelength of the Doppler-shifted second harmonic of RTS provides a means to estimate intensities between 1018 W/cm2 and 1019 W/cm2.  We also comment on measurements of the angular distribution of RTS and its potential as a laser intensity gauge.

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