Events at Physics |
Events on Thursday, April 16th, 2009
- R. G. Herb Condensed Matter Seminar
- Quantum Control and Measurement of Spins in Cold Atomic Gases
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Ivan Deutsch, University of New Mexico
- Abstract: Spins are the natural carriers of quantum information given their long coherence times and the mature methods for controlling them with coherent rf. Spins in atomic gases are of particular interest given their further isolation from a thermal condensed matter environment and our ability to manipulate them optically. Laser cooling and trapping, optical pumping, coherent Raman interactions, and polarization spectroscopy are all tools in the arsenal that can be put to work. In this talk I will review a series of developments in quantum control and measurement of spins in laser-cooled atomic samples, with an eye towards quantum information processing. In collaboration with Poul Jessen, College of Optical Science, University of Arizona, we have designed and implemented tools for arbitrary state preparation in a large-dimensional hyperfine manifold, and quantum-state reconstruction in a single shot based on continuous weak measurement. We have extended this control to the design of arbitrary unitary maps, which will allow qudit logic on large spins. Finally, the coherent interaction between spins is essential for scalable quantum information processing. I will show how one perform quantum logic gates between nuclear spins over tens of nanometers based on optical Feshbach resonances in alkaline-earth-like atoms.
- Host: Mark Saffman
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- High Energy Cosmic Rays with CREAM, Fermi, and Beyond
- Time: 2:00 pm
- Place: 5280 Chamberlin
- Speaker: Terri J. Brandt, Ohio State University
- Abstract: The origins, acceleration mechanism(s), and propagation of high energy cosmic rays within the galaxy have been a mystery for nearly 100 years. Today's experiments are beginning to provide a more complete and definitive answer to these classic questions. I will discuss one such: the Cosmic Ray Energetics And Mass (CREAM) balloon-borne experiment. CREAM uses a complementary set of charge, energy, and tracking detectors on successive balloon flights around the Antarctic continent to directly measure individual CR nuclei's spectra over 5 orders of magnitude in energy. These spectra provide clues to CR origins and acceleration mechanisms. To better understand CR propagation, we have extended the Boron to Carbon ratio over an order of magnitude higher in energy than previous measurements. I will then explore a few ways ongoing and upcoming detections of CR signatures with gamma-ray and neutrino detectors may shed further light on the classic CR questions, both through direct and indirect detection.
- Host: Albrecht Karle
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Quark Matter in Neutron Stars
- Time: 4:00 pm
- Place: 4274 Chamberlin
- Speaker: Mark Alford, Washington University
- Abstract: Quark matter at high density and low temperature is expected to be a color superconductor, which is a degenerate Fermi gas of quarks with a condensate of Cooper pairs near the Fermi surface. At the highest densities, where the QCD coupling is weak, rigorous calculations are possible, and the ground state is a particularly symmetric state, the color-flavor locked (CFL) phase. At lower densities the CFL phase suffers from flavor-symmetry-breaking stresses, so alternative phases,
some of which break translation and/or rotation invariance, may be favored. I will review the state of our understanding of these phenomena, and discuss the effort to develop signatures of the presence of color superconducting quark matter in neutron stars.
- Host: Michael J. Ramsey-Musolf