Mar
05
Teaser:

Matter placed in a strong magnetic field provides a fascinating laboratory in which to study exotic quantum phenomena in a highly controllable manner.  This talk will summarize our recent findings of novel magnetic properties of carbon nanotubes, graphene, and graphite, probed via high-field magneto-optical spectroscopy.  A magnetic field applied parallel to a nanotube introduces an Aharonov-Bohm phase to the electronic wave function, which leads to band gap oscillations, magnetic brightening of dark excitons, and extremely large magnetic...

Mar
04
Teaser:

The ATLAS Experiment at the Large Hadron Collider with its sister experiment CMS reported a discovery last summer of a new boson which is consistent with the Standard Model Higgs boson.  The Higgs particle has been searched for decades. It is the final jewel in the Standard Model of particle physics, a crowning achievement of 20th century science that gives a powerful understanding of fundamental particles and their interactions. In the Standard Model, the Higgs is the quantum of a field that accounts for the masses of those particles.  We will describe the apparatus, the data and other searches....

Mar
04
Teaser:

The ATLAS Experiment at the Large Hadron Collider with its sister experiment CMS reported a discovery last summer of a new boson which is consistent with the Standard Model Higgs boson.  The Higgs particle has been searched for decades. It is the final jewel in the Standard Model of particle physics, a crowning achievement of 20th century science that gives a powerful understanding of fundamental particles and their interactions. In the Standard Model, the Higgs is the quantum of a field that accounts for the masses of those particles.  We will describe the apparatus, the...

Feb
28
Teaser:

The control of quantum systems is limited by unwanted interactions with the environment and uncertainties in the applied control fields.  For ions these uncertainties include unwanted fluctuations in the intensity and the frequency of the electromagnetic field used to control the qubit. For unknown but static errors on the time scale of the experiment, compensating composite pulses sequences can be used to minimize the effect of these errors. In this talk, I will describe the general method of compensating composite pulse sequences for single qubit and multi-qubit systems. I will...

Feb
26
Teaser:

The physics of granular flow is of widespread practical and fundamental interest, and is also important in geology and astrophysics. One challenge to understanding and controlling behavior is that the mechanical response is nonlinear, with a forcing threshold below which the medium is static and above which it flows freely. Furthermore, just above threshold the response may be intermittent even though the forcing is steady. Two familiar examples are avalanches on a heap and clogging in a silo. Another example is dynamical heterogeneities for systems...

Feb
25
Teaser:

What could possibly be new in the Ising model, arguably the most-studied model of statistical physics?  Plenty!  Consider the Ising model initially at
infinite temperature that is suddenly cooled to zero temperature and evolves by single spin-flip dynamics.  What happens?  In one dimension, the ground state is always reached and the evolution can be solved exactly.  In two dimensions, the ground state is reached only about 2/3 of the time, and the long-time evolution is characterized by two distinct time scales, the longer of which arises from topological defects...

Feb
20
Teaser:

PLEASE NOTE: This is a WEBINAR

We investigate the effect of anharmonicity and interactions on the dynamics of an initially Gaussian wavepacket in a weakly anharmonic potential. We find that repeated perturbations can create revivals, echoes, and revival-echoes, with properties that can be controlled via the strength and symmetry of the perturbations.  We also find that depending on the strength and sign of interactions and anharmonicity, the quantum state can be either...

Feb
18
Teaser:

I present inelastic neutron scattering data from one- two- and three-dimensional insulating magnetic materials at low temperatures that do not display a coherent resonant mode of excitation. Instead, momentum resolved spectra take the form of bounded continua. I interpret the spectra as evidence for fractionalization of a spin flip into distinct quasi-particles.

Feb
14
Teaser:

The U.S. Naval Observatory provides the master clock for the DoD.  To support this mission, we have built and fielded 4 rubidium atomic fountain clocks at our Washington D.C. site.  This ensemble of clocks has been running continuously for slightly less than two years and is contributing to our larger ensemble of atomic clocks.

Feb
12
Teaser:

Many organisms fly in order to survive and reproduce. I am fascinated by the mechanics of flying birds, insects, and autorotating seeds. Their development as an individual and their evolution as a species are shaped by the physical interaction between organism and surrounding air. It is critical that the organism’s architecture is tuned for propelling itself and controlling its motion. Flying macroscopic animals and plants maximize performance by generating and manipulating vortices. These vortices are created close to the body as it is driven by the action of muscles or gravity, then are...

Feb
11
Teaser:

A quantum processor,  using quantum states of light and matter, holds the promise of performing calculations and simulations that are not practical by a classical processor. Many of the key components for a quantum processor have been demonstrated by various research groups and we can expect these components to be integrated into basic quantum processors in the near future. However, there remain significant technical challenges in scaling the system size and making the system robust and flexible. In GTRI ‘s Quantum Information Systems (QIS)  Group, we use...

Feb
07
Teaser:

Low-luminosity GRBs or X-ray flashes (XRFs), which often accompany supernovae, are typically ascribed to either the supernova shock breakout or weak GRBs powered by the central engine of stellar mass. We propose the tidal disruption of a white dwarf (WD) by an intermediate-mass black hole (IMBH) as another channel for XRFs. Such disruptions last for 100-5000 seconds.  The release of gravitational energy over short time generates a powerful flare. The magnetic field is quickly amplified in the fallback material, and then the BH launches a slow uncollimated jet. The emission from jet photosphere dominates X-...

Feb
06
Teaser:

PLEASE NOTE: This is a WEBINAR

Loose sand particles can jam together to become a solid. Think of the dry sand on the beach: it supports your weight so you can walk on it – you don't need to swim in sand. Jammed sand indeed so much resists deformation that it even expands when you try to make it flow. This was already discovered by Osborne Reynolds in 1885. In fact, you can make sand particles jam by making them flow in a container that cannot expand. This effect is known as shear jamming and was discovered only recently. We have now studied the...

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