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Events at Physics

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Events on Thursday, October 22nd, 2015

R. G. Herb Condensed Matter Seminar
Programmable nonreciprocity in multi-mode parametric devices
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Dr. Leonardo Ranzani, BBN/Raytheon
Abstract:
Josephson Parametric Amplifiers (JPAs) can perform quantum-limited
readout of superconducting qubits. However, since they are
reflection-based amplifiers, an external RF circulator is always
necessary to suppress back-action. A new approach is to use directional
parametric amplification by driving multiple parametric processes
simultaneously with different pump phases. SQUID and SLUG amplifiers in
fact operate by a similar mechanism: the interference between parametric
processes driven by internal oscillations at the Josephson frequency
suppresses the reverse gain and explains the high level of isolation in
this devices. In this talk I am going to discuss a general approach to
the study of parametric devices driven by multiple pump signals. As
opposed to traditional JPAs, where only two modes, signal and idler,
interact, in multi-pump devices three or more modes are pumped
simultaneously. I will show how to use directed graphs to compute the
scattering properties of such multi-mode devices and design parametric
nonreciprocal components, including circulators and directional amplifiers.
Host: McDermott
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Cosmology Journal Club
An Informal discussion about a broad variety of arXiv papers related to Cosmology
Time: 12:15 pm
Place: 5242 Chamberlin Hall
Abstract: Please visit the following link for more details:
http://cmb.physics.wisc.edu/journal/index.html
Please 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 Amol Upadhye (aupadhye@wisc.edu).
Host: Amol Upadhye
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Astronomy Colloquium
Bautz Lecturer
"Exoplanetary Science's Kepler Revolution"
Time: 3:45 pm
Place: 4421 Sterling hall, Coffee and Cookies at 3:30 PM
Speaker: Professor John Johnson , Harvard CfA
Abstract: Just four years ago the prospect of finding rocky planets around other stars was still the subject of science fiction—none had been found and reasonable estimates put us decades away from such momentous discoveries. All of that has changed very recently on the heels of the extraordinarily successful NASA Kepler mission. I will provide an overview of Kepler science and the new view it has provided us on the demographics of exoplanets throughout the Galaxy. In addition to the statistics of exoplanets, I will also show highlights from the many unusual individual discoveries that have expanded our understanding of planet formation and allowed us to view our Solar System within a much broader context than ever before, including: Hundreds of new planets from the extended Kepler K2 Mission, a disintegrating planetesimal orbiting a white dwarf, and updates on the number of (and nearest) Earth-like, habitable zone planets in the Galaxy.
Host: Eric Wilcots
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