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: No Class

Physics 838 Seminar
04.20.2020 4:00 pm - 5:00 pm
John S. Toll Rm 1201


Speaker 1: Haonan Xiong

Title: High coherence fluxonium qubit and microwave-activated entangling gates

We report experimental progress on microwave-activated entangling gates with capacitively coupled fluxonium qubits. When biased at the flux sweet-spot, individual qubit transition has long coherence (the best device has T2 > 400 us) [1]. A control-Z gate can be implemented by sending a short 2π-pulse at the frequency near the 1→2 transition of the target qubit [2]. The gate transition has higher frequency and larger matrix element than the qubit transition, resulting in fast gate and minimal spurious phase errors. Another microwave entangling gate, similar to the cross-resonance gate in transmon [3], can be applied to the computational subspace. We discuss qubits' design and fabrication, initialization, readout, and benchmarking of the gates.

[1] Long B. Nguyen, et. al., Phys. Rev. X (2019).
[2] Konstantin N. Nesterov, et. al., Phys. Rev. A 98, 030301 (2018).
[3] Jerry M. Chow, et. al., Phys. Rev. Lett. 107, 080502 (2011).

Speaker 2:Jingnan Cai

Title: Chaos and Chimeras in Hysteretic RF SQUID Metamaterials

Radio frequency Superconducting Quantum Interference Device (rf SQUID) has been established as a viable building block for microwave frequency metamaterials [1,2]. The rf SQUID resonance is tunable under applied dc flux, with upper-frequency range scaling as1+rf . Our previous design restricted the parameter rf below unity to avoid hysteresis, thus limited the resonance range. We have built new arrays of RF SQUID meta-atoms in the hysteretic regime to explore their interesting properties with the ultimate goal of extending the resonance frequency tunability. Much theoretical work has predicted chaotic dynamics and chimera states in such systems. Results from microwave transmission measurements showing signs of these phenomena will be reported. We will also discuss the future work of observing chimera in laser scanning microscopy  [3]. This work is supported by DOE through grant # DESC0018788.

[1] Phys. Rev. X, 3, 041029 (2013)

[2] Phys. Rev. X, 5, 041045 (2015)

[3] Appl. Phys. Lett. 114, 082601 (2019)