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Events During the Week of March 19th through March 26th, 2017

Monday, March 20th, 2017

R. G. Herb Condensed Matter Seminar
Revealing quantum behavior with coupled superconducting devices
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Prof. Nadav Katz, Racah Institute of Physics, Hebrew University of Jerusalem
Abstract: I will present two projects, based on coupled superconducting resonator devices:
1. Atomic sized two-level systems (TLSs) in dielectrics are known as a major source of loss in superconducting devices, particularly due to frequency noise. However, the induced frequency shifts on the devices, even by far off-resonance TLSs, is often suppressed by symmetry when standard single-tone spectroscopy is used. We introduce a two-tone spectroscopy on the normal modes of a pair of coupled superconducting coplanar waveguide resonators to uncover this effect by asymmetric saturation. Together with an appropriate generalized saturation model this enables us to extract the average single-photon Rabi frequency of dominant TLSs to be Ω0/2π≈79 kHz. At high photon numbers we observe an enhanced sensitivity to nonlinear kinetic inductance when using the two-tone method and estimate the value of the Kerr coefficient as K/2π≈−1×10−4 Hz/photon. Furthermore, the life-time of each resonance can be controlled (increased) by pumping of the other mode as demonstrated both experimentally and theoretically.

2. Multiple bosons undergoing coherent evolution in a coupled network of resonators constitute a so-called quantum walk system. The simplest example of such a two-particle interference is the celebrated Hong-Ou-Mandel interference. When scaling to larger boson numbers, simulating the exact distribution of bosons has been shown, under reasonable assumptions, to be exponentially hard. We analyze the feasibility and expected performance of a globally connected superconducting resonator based quantum walk system, using the known characteristics of state-of-the-art components. We simulate the sensitivity of such a system to decay processes and to perturbations and compare with coherent input states.
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 - 1:15 pm
Place: 5242 Chamberlin Hall
Abstract: Please visit the following link for more details:
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 (
Host: Amol Upadhye
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Tuesday, March 21st, 2017

Theory Seminar (High Energy/Cosmology)
Relaxion from particle production
Time: 3:30 pm
Place: 5280 Chamberlin
Speaker: Gustavo Marques Tavares, Stanford University
Abstract: Recently a new solution to the hierarchy problem was proposed which makes use of the cosmological evolution of a light scalar field, a scanner, instead of symmetry or anthropic arguments to select a small Higgs mass. In the original proposal this scanner field could be the QCD axion and thus such class of solution became known as ``relaxion’’. Two central features required of the relaxion are a reason for why a small Higgs mass is special from the scanner’s viewpoint and a mechanism fo the scanner to dissipate its energy in order to stop in a value associated with small Higgs mass. In this talk we propose a novel mechanism that achieves both goals and opens new possibilities for the relaxion. We show that particle production can create an effective friction force for the relaxion and show how it can be used to ``select’’ the TeV scale as a special energy scale from reasonable initial conditions. This allows for the scanning to happen much faster than in previous relaxion models, which usually require very large amounts of inflation, and also allows for the scanning to take place after inflation has ended.
Presentation: gmt-relaxion.pdf
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Wednesday, March 22nd, 2017

No events scheduled

Thursday, March 23rd, 2017

Atomic Physics Seminar
Time: 8:00 am - 6:00 pm
Place: 2241 Chamberlin hall
Speaker: Mark Saffman, et al.
Host: Mark Saffman
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Friday, March 24th, 2017

Atomic Physics Seminar
Rydberg crystals in a cold lattice gas
Time: 2:00 pm - 3:00 pm
Place: 5310 Chamberlin Hall
Speaker: Prof. David Petrosyan, Institute of Electronic Structure & Laser (IESL) Foundation for Research and Technology - Hellas (FORTH) Heraklion, Crete, GREECE
Abstract: Strong, long-range interactions between atoms in high-lying Rydberg states
make them attractive systems for the studies of ordered phases of interacting
many-body systems and simulating quantum phase transitions.

Several conceptually different approaches have been explored, both theoretically
and experimentally, for the preparation of crystalline order of Rydberg excitations
in spatially-extended ensembles of cold atoms. These include direct (near-)resonant
laser excitation of strongly-interacting Rydberg states in a two-dimensional lattice
gas, and adiabatic preparation of crystalline phases of Rydberg excitations in a
one-dimensional optical lattice by adiabatic frequency sweep of the excitation laser.
We show, however, that taking into account realistic relaxation processes affecting
the atoms severely complicates the prospects of attaining sizable crystals of Rydberg
excitations in laser-driven atomic media. Our simulations well reproduce the
experimental observations of spatial ordering of Rydberg excitations in driven
dissipative lattice gases, as well as highly sub-Poissonian probability distribution
of the excitation number. We find that the excitations essentially form liquid rather
than crystal phases with long-range order.
Host: Mark Saffman
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