Events at Physics
Events During the Week of November 13th through November 19th, 2011
- Condensed Matter Theory Group Seminar
- Interaction effects on localization
- Time: 4:30 pm
- Place: 5310 Chamberlin
- Speaker: Peter Wölfle, Karlsruhe Institute of Technology, Germany
- Abstract: Anderson localization is influenced by interaction effects in various ways. First, interaction processes destroy the phase coherence and limit localization at finite temperature in all dimensions. Secondly, interaction gives rise to a new type of quantum correction to the conductivity. Thirdly, the metal-insulator transition is modified by interaction effects in ways not completely understood yet. I review the renormalization group theory of disordered interacting electron systems. Finally, a comparison with experimental data on selected systems is presented.
- Host: Perkins
- Chaos & Complex Systems Seminar
- Teaching computers to extract complex information from news articles
- Time: 12:05 pm
- Place: 4274 Chamberlin
- Speaker: Jude Shavlik, Jude Shavlik, UW Department of Computer Science
- Host: Sprott
- Department Meeting
- Time: 12:15 pm
- Place: 5280 Chamberlin Hall
- MEETING CANCELED
- R. G. Herb Condensed Matter Seminar
- Resonant Passage of Spin States in a Triple Quantum Dot
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Xuedong Hu, University of Buffalo
- Abstract: Experimental and theoretical research on spin qubits in quantum dots are progressing toward systems with multiple spins in multiple dots. Among the many quantum information processing tasks that can be accomplished by such a multi-qubit system is the coherent transfer of quantum states on chip, which is an essential capability of a practical quantum computer. In this talk I will discuss our recent work on the physics of adiabatic quantum teleportation in a triple dot system. In particular, we show that a teleportation process over a three-spin chain can be mapped exactly onto two parallel and coherent adiabatic passages, one for each spin orientation. When the time evolution is not adiabatic, we find that the fidelity of information transfer displays a strong oscillatory behavior, and it is possible to have high fidelity when the switching frequency of the qubit interactions is a subharmonic of the characteristic energy splitting of the three-spin system. This resonant operation of an adiabatic passage protocol of spin states is both fast and robust, and points to a new way to perform other quantum gates.
- Host: Coppersmith
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Magic, precise, and electroweak
- Time: 2:30 pm
- Place: 4274 Chamberlin Hall
- Speaker: Andrei Derevianko, University of Nevada-Reno
- Abstract: Precision timepieces are marvels of human ingenuity. Over the past half-a-century, precision time-keeping has been carried out with atomic clocks. I will review a novel and rapidly developing class of atomic clocks, optical lattice clocks. At their projected accuracy level, these would neither lose nor gain a fraction of a second over estimated age of the Universe. In other words, if someone were to build such a clock at the Big Bang and if such a timepiece were to survive the 14 billion years, the clock would be off by no more than a mere second. I will also talk about the next frontier: nuclear clock.
In the second part I will overview atomic searches for new physics beyond the Standard Model of elementary particles. I will report on a refined analysis of table-top experiments on violation of mirror symmetry in atoms that sets powerful constraints on a hypothesized particle, the extra Z-boson. Our raised bound on the Z' masses improves upon the Tevatron results and carves out a lower-energy part of the discovery reach of the Large Hadron Collider.
- Host: Mark Saffman
- Graduate Introductory Seminar
- Condensed Matter Experimental Seminar
- Time: 5:30 pm
- Place: 2223 Chamberlin Hall
- Speaker: Eriksson, Himpsel, Lagally, McDermott, Onellion, Rzchowski, Winokur
- Cosmology Journal Club
- An Informal discussion about a broad variety of arXiv papers related to Cosmology
- Time: 12:00 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 Le Zhang (firstname.lastname@example.org)
- Host: Peter Timbie
- Physics Department Colloquium
- Condensation of excitons and polaritons
- Time: 3:30 pm
- Place: 2241 Chamberlin Hall (coffee at 4:30 pm)
- Speaker: Peter Littlewood, Argonne National Laboratory
- Abstract: Macroscopic phase coherence is one of the most remarkable manifestations of quantum mechanics, yet it seems to be the inevitable ground state of interacting many-body systems. In the last two decades, the familiar examples of superfluid He and conventional superconductors have been joined by exotic and high temperature superconductors, ultra-cold atomic gases, both bosonic and fermionic, and recently systems of excitons, magnons, and exciton-photon superpositions called polaritons, the subject of this talk.
An exciton is the solid-state analogue of positronium, made up of an electron and a hole in a semiconductor, bound together by the Coulomb interaction. The idea that a dense system of electrons and holes would be unstable toward an excitonic (electrical) insulator is one of the key ideas underlying metal-insulator transition physics. The further possibility that an exciton fluid would be a Bose-Einstein condensate was raised over 40 years ago, and has been the subject of an extensive experimental search in a variety of condensed matter systems. Such a condensate would naturally exhibit phase coherence. Lately, some novel experiments with planar optical microcavities make use of the mixing of excitons with photons to create a composite boson called a polariton that has a very light mass, and is thus a good candidate for a high-temperature Bose condensate. Good evidence for spontaneous coherence has now been obtained, though there are special issues to resolve considering the effects of low dimensionality, disorder, strong interactions, and especially strong decoherence associated with decay of the condensate into environmental photons---since the condensate is a special kind of laser.
- Host: Perkins