Events Archive

Sep
07
2011
"Measuring Everything You've Always Wanted to Know About a Laser Pulse"
Measuring an event in time seems to require a shorter one. As a result, the development of a technique for measuring ultrashort laser pulses—the shortest events ever created—has been particularly difficult. We have, however, developed simple methods for fully characterizing these events, that is, for measuring a pulse's intensity and phase vs. time. One involves making an optical spectrogram of the pulse by using nonlinear optic. The mathematics involved is equivalent to the two-dimensional phase-retrieval problem—a problem that’s solvable because the Fundamental Theorem of Algebra fails for polynomials of two variables.  We call...
Sep
01
2011
"Radio pulse measurements of high energy neutrinos: ANITA and ARA experiments"
We'll look at two novel experiments that are looking for ultrahigh energy neutrinos in the Antarctic ice. ANITA is a balloon-borne experiment which has twice flown over Antarctica making observations of ultrahigh energy cosmic rays and neutrinos. ARA is a new englacial project, under construction at the South Pole with similar goals. Both utilize the Askaryan Effect, coherent radio Cherenkov emission from particle cascades in matter, for neutrino detection.
Aug
31
2011
Annual School of Physics Gathering
Aug
29
2011
"Simulating condensed matter systems with interacting photons"
Photons do not interact strongly in nature, and have thus been relegated to a role as a tool rather than an object of study in condensed matter physics.However, in cavity quantum electrodynamics, the strong interaction of light with a single atom can lead to strong atom-mediated photon-photoninteractions, even when the light and atomic transitions are not resonant. Recent theoretical proposals have predicted phase transitions in arrays ofthese cavities, demonstrating that complex matter-like phenomena can emerge from a sea of interacting photons. I will present our recent measurements demonstrating strong photon-photon interactions in superconducting cavity QED...
Aug
24
2011
"Vulcanized matter: Its statistics, its physics, and its statistical physics"
As Goodyear discovered, when he first vulcanized rubber in 1839, a viscous liquid of macromolecules becomes an unusual, utterly random, solid, provided that enough chemical bonds are introduced between the molecules.  Perhaps surprisingly, given the randomness of their architectures, solids formed by the vulcanization process exhibit a number of rather simple and universal features -- both structural and elastic -- that are not exhibited by the apparently simpler, crystalline solids.  In this colloquium, I shall give an overview of current approaches to the physical properties of vulcanized matter and other random-network-forming media, paying special attention to...
Jun
23
2011
"The NINJA project"
Two important advances have occurred in recent years which have brought us closer to the goal of observing and interpreting gravitational waves from coalescing compact objects: the successful construction and operation of a world-wide network of ground-based gravitational-wave detectors and the impressive success of numerical relativity in successfully simulating the merger phase of Binary Black Hole (BBH) coalescence. The aim of the Numerical INjection Analysis (NINJA) project is to study the sensitivity of gravitational-wave analysis pipelines to numerical simulations of waveforms and foster close collaboration between numerical relativists and data analysts.  NINJA-1 was a huge...
May
25
2011
5th Southeast Meeting on Soft Materials
This workshop brings together researchers with an interest in soft materials, fluids, and biophysics to discuss their work and explore partnerships. All participants may present a sound bite (a few minutes).  The day will include breakfast, lunch, and coffee. Registration is free, but required. Invited Speakers include M. Cristina Marchetti (Keynote Speaker, Syracuse University), Paul Goldbart (Georgia Tech), Juana Mendenhall (Morehouse College), Elisa Riedo (Georgia Tech), Susanne Ullrich (University of Georgia). Location: Georgia Tech, Marcus Nanotechnology Building, Room 1116Registration...
May
24
2011
"From Lattice QCD to Graphene and Ultracold Fermi Gases"
Obtaining a priori information on strongly interacting many-fermion systems remains a challenging problem in theoretical physics. A promising way forward is the use of Monte Carlo simulations, which are non-perturbative and take full account of quantum fluctuations. A famous example is Lattice QCD, which aims to elucidate the interactions between quarks and gluons at low energies, where QCD is strongly coupled. I will provide an updateon the application of such methods to closely related problems in condensed matter and atomic physics, highlighting modern computational and algorithmic developments. Specific examples include graphene and strongly coupled ultracold Fermi gases.
May
19
2011
"Discrete breathers and the anomalous decay of luminescence"
Some years ago an anomaly was noted in the decay of luminescence in certain doped alkali halides. The anomaly was eventually explained using a factor of a billion slowdown in lattice relaxation, a remarkable stretching of time scales. This slowdown was found to be caused by the creation of a ‘breather’ in the neighborhood of the dopant. Discrete breathers are nondispersive classical excitations that are known to be significant in many natural systems. In the talk I focus on the occurrence of breathers in doped alkali halides. Several more general properties of breathers have arisen from this study, among them is the quantum breather...
Apr
21
2011
"Coupled quantized harmonic oscillators" by Kenton Brown
In theory, quantum computers can solve certain problems much more efficiently than classical computers. This possibility has motivated experimental efforts to construct devices that manipulate quantum bits (qubits) in a variety of physical systems. One such system is composed of atomic ions confined by electric fields in a rf Paul trap. The motions of such ions can be modeled to a very good approximation as harmonic oscillators, and with suitable laser cooling techniques they can be cooled to the harmonic oscillator ground state. When trapped within the same potential minimum, ions interact strongly via the Coulomb force, thereby enabling multiple-qubit quantum gates that are...

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