Events at Physics
Events on Thursday, October 31st, 2019
- R. G. Herb Condensed Matter Seminar
- Wrestling with ultrastrongly coupled parasitic modes in circuit quantum electrodynamics
- Time: 11:00 am
- Place: 5310 Chamberlin Hall
- Speaker: Dr. Ivan Pechenezhskiy , University of Maryland
- Abstract: Several promising superconducting qubit designs, including the protected ones, require superconductors operating as perfect inductors at microwave frequencies. As the value of the inductance increases with the inductor length, so does the parasitic capacitance due to the spatial extension of the inductor. Parasitic self-resonances formed this way impede the potential applications of extremely large inductances. Even in the simplest superconducting qubit circuit, in which a Josephson junction is shunted by a hyperinductor, the distributed nature of parasitic capacitance leads to an ultrastrong coupling of the parasitic modes to the qubit. This ultrastrong coupling of the parasitic modes prevents a perturbation theory treatment of the qubit excitation spectra. While a complete quantum description of the underlying qubit circuit is computationally prohibitive, diagonalization of an effective multi-mode Hamiltonian reproduces the experimental data both below and above the lowest parasitic modes. On the experimental side, the effects of the parasitic modes can be partially mitigated by releasing the qubit circuit off the substrate. This trick enables the realization of a new qubit design — blochnium.
- Host: McDermott
- Cosmology Journal Club
- Time: 12:00 pm
- Place: 5242 Chamberlin Hall
- Abstract: Please visit the following link for more details:
Feel free to bring your lunch!
If you have questions or comments about this journal club, would like to propose a topic or volunteer to introduce a paper, please email Ross Cawthon (firstname.lastname@example.org) and Santanu Das (email@example.com).
- Astronomy Colloquium
- "Suppressed Superwinds: A New Paradigm for Extreme Massive-Star Feedback”
- Time: 3:30 pm
- Place: 4421 Sterling Hall, Coffee and cookies 3:30 PM, Talk begins 3:45 PM
- Speaker: Sally Oey, University of Michigan
- Abstract: Feedback from young, super star clusters (SSCs) is a major driver for galaxy evolution at all cosmic epochs, but may be especially relevant for cosmic reionization. The standard scenario for massive-star feedback has been that superwinds from SSCs clear pathways for Lyman continuum (LyC) and Ly-alpha radiation to escape from host galaxies. However, theoretical predictions indicate that for the most massive and compact SSCs, superwinds are actually suppressed by catastrophic cooling and pressure confinement. These extreme conditions are rare, but observational evidence from local starbursts increasingly supports this scenario. I will present our work in establishing this new paradigm and its consequences for LyC and Ly-alpha escape.
- Host: Professor Amy Barger