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Events During the Week of April 10th through April 17th, 2016

Monday, April 11th, 2016

Condensed Matter Theory Group Seminar
Non-ergodicity in many body systems and the phase diagram of Josephson junction chains
Time: 10:00 am
Place: 5280 Chamberlin Hall
Speaker: Lev Ioffe, Rutgers
Abstract: At very high disorder a generic closed quantum systems becomes completely localized. I argue that this (many body) localization is preempted by a wide regime of non-ergodic behavior that displays a number of unusual properties. A good system to study these effects are Josephson junction arrays in a somewhat unusual regime.
I review the physics of Josephson arrays and the general problem of the superconductor-insulator transition in these structures. In the main part of the talk I will focus on the novel phases appearing in one-dimensional Josephson junction chains at relatively high temperatures. I will argue that these phases are robust with respect to the presence of the ubiquitous random charges and thus allow experimental observation. I show that at finite temperatures both ordered and disordered chains display a dynamical transition to the many body localized state. While resistivity is strictly infinite in the many body localized state, it is exponentially large in the intermediate non-ergodic bad metal. I will discuss the possibility of experimental observation of these transitions.
Host: Robert Mcdermott
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Plasma Physics (Physics/ECE/NE 922) Seminar
Generation and Reconnection of Magnetic Field in Colliding Laser High Energy-Density Plasmas
Time: 12:00 pm - 1:00 pm
Place: 1153 Mechanical Engineering
Speaker: Dr. Gennady Fiksel, University of Michigan
Host: UW Madison
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Department Meeting
Time: 4:00 pm - 5:00 pm
Place: 4274 Chamberlin Hall
Host: Albrecht Karle
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Tuesday, April 12th, 2016

R. G. Herb Condensed Matter Seminar
Out-of -time-order correlators in solid state physics
Time: 10:00 am
Place: 5280 Chamberlin Hall
Speaker: Lara Faoro, CNRS
Abstract: Out-of-time-order correlators, introduced recently in the context of quantum gravity describe the delocalization of information in quantum systems. <br>
In classical chaotic systems, these correlators are known to grow exponentially with the Lyupanov exponent. I discuss the behavior of these correlators in canonical examples of solid state quantum chaotic systems: disordered electrons with and without phonon interaction. In conclusion, I discuss possible measurements of these correlators in superconducting systems.
Host: Robert Mcdermott
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Chaos & Complex Systems Seminar
Data centric computing in emerging nonvolatile memory technologies
Time: 12:05 pm - 1:00 pm
Place: 4274 Chamberlin Hall (refreshments will be served)
Speaker: Jing Li, Department of Computer Sciences
Abstract: The confluence of disruptive technologies beyond CMOS and "Big Data" workloads calls for a fundamental paradigm shift from homogenous compute-centric system to heterogeneous data-centric system for better innovation, competition and productivity. With the objective of rethinking data-centric system from ground up, through a concrete example, I will show how to leverage emerging memory technology such as phase-change memory (PCM) to realize a new IC building block for future data-centric system. A novel chip was designed and fabricated for the first time, blurring the boundary between computation and storage, i.e., it can either be configured as a compute unit - a high performance search engine or as a storage media - storage class memory. It achieves >10x area reduction compared to homogenous CMOS-based design at the same technology node and reliably operates at ultra-low voltage down to 750mV. In the talk I will briefly highlight a few critical enabling techniques from material, circuit, architecture and algorithm perspectives. I will also highlight the major research activities in my lab in developing collaborative software/hardware solutions to address classical von Neumann bottlenecks.
Host: Clint Sprott
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Wednesday, April 13th, 2016

Department Meeting
Time: 12:15 pm
Place: 5310 Chamberlin Hall
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Thursday, April 14th, 2016

R. G. Herb Condensed Matter Seminar
Dynamically corrected entangling gates for spin qubits
Time: 10:00 am
Place: 5310 Chamberlin Hall
Speaker: Jason Kestner, UMBC
Abstract: Spin qubits have recently demonstrated high fidelity single-qubit rotations and relatively long coherence times in a variety of experiments. High fidelity two-qubit entangling operations are the next challenge on the path towards scalable universal quantum computation. In this talk, we present recent theoretical results for dynamical decoupling protocols that protect the generation of entanglement. For capacitive coupling, we show that access to a particular set of high-fidelity single-qubit gates is sufficient to eliminate a large portion of the coherent error coming from low-frequency hyperfine and charge noise during the basic two-qubit operation, bringing CNOT gate fidelity up to the level of single-qubit gate fidelities. We will also discuss how to produce the basic entangling operation and the necessary single-qubit operations, as well as extensions to other coupling types.
Host: Coppersmith
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Cosmology Journal Club
An Informal discussion about a broad variety of arXiv papers related to Cosmology
Time: 12:15 pm - 1:15 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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Friday, April 15th, 2016

Department Meeting
Closed Department Meeting
Time: 12:00 pm - 1:00 pm
Place: 5280 Chamberlin Hall
Speaker: Albrecht Karle
Closed meeting to discuss personnel matters—pursuant to Section 19.85(1)(c) of the Wisconsin Open Meetings Law.
Host: Albrecht Karle
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Theory Seminar (High Energy/Cosmology)
D6-branes, axion monodromy inflation and moduli backreaction
Time: 2:00 pm - 3:00 pm
Place: 5280 Chamberlin Hall
Speaker: Aitor Landete, Instituto de Fisica Teorica, Madrid
Abstract: We develop new scenarios of large field inflation in type IIA string compactifications in which the key ingredient is a D6-brane that generates a bilinear superpotential which couples the brane position modulus to a Kahler modulus. This feature allows us to construct two different models where the inflaton candidate could be the B-field axion or the D6-brane Wilson Line where all the remaining moduli are stabilized supersymmetrically. The scalar potential has the multi-branched structure typical of F-term axion monodromy models and, near its supersymmetric minima, it is described by a 4d supergravity model of chaotic inflation with a stabilizer field. Finally we analyze the effects, in our model, of integrating out the relevant closed string moduli consistently.
Host: Pablo Soler
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Physics Department Colloquium
Probing the Accelerating Universe with the Dark Energy Survey
Time: 3:30 pm - 4:30 pm
Place: 2241 Chamberlin Hall
Speaker: Josh Frieman, Fermilab and the University of Chicago
Abstract: The Nobel Prize in Physics for 2011 was awarded for the discovery that the expansion of the Universe is accelerating. Yet the physical origin of cosmic acceleration remains a mystery. The Dark Energy Survey (DES) aims to address the questions: why is the expansion speeding up? Is cosmic acceleration due to dark energy or does it require a modification of General Relativity? If dark energy, is it the energy density of the vacuum (Einstein's cosmological constant) or something else? DES is addressing these questions by measuring the history of cosmic expansion and of the growth of structure through four complementary techniques: galaxy clusters, the large-scale galaxy distribution, weak gravitational lensing, and supernovae. The DES collaboration built a new, 570-megapixel, digital camera for the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory in Chile to carry out a deep, wide-area sky survey of 300 million galaxies and a time-domain survey that will discover several thousand supernovae. I will overview the DES project, which achieved `first light' in September 2012 and which recently completed its third of five survey seasons, and will describe a number of early science results from the solar system to distant quasars.
Host: Kam Arnold
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