Events at Physics |
Events on Thursday, September 17th, 2009
- R. G. Herb Condensed Matter Seminar
- Optimal quantum gates in imperfect qubits
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Frank Wilhelm, University of Waterloo & ICQ
- Abstract: Physical qubits are necessarily not perfect: they typically contain higher levels beyond the two-state Hilbert space of a qubit and couple to decoherence mechanisms. We show how optimal control theory helps to accommodate these imperfections and still realize fast high-fidelity quantum gates. For the case of a weakly anharmonic multilevel system containing a qubit, we introduce the derivative removal by adiabatic gate (DRAG) technique that retains adiabaticity even for fast gates. This technique allows improvement of gate fidelity in realistic superconducting setups by an order of magnitude beyond the present state of the art and to get close to the fault-tolerance threshold [1] and beyond, if multiple carrier frequencies are used. In the case of non-Markovian decoherence, optimal gates are extremely short Rabi bursts at the optimum working point, which are modulated to refocus counter-rotating terms [2].
[1] F. Motzoi, J. M. Gambetta, P. Rebentrost, and F. K. Wilhelm, Phys. Rev. Lett., in press, arXiv:0901.0534.
[2] P. Rebentrost, I. Serban, T. Schulte-Herbrueggen, and F. K. Wilhelm, Phys. Rev. Lett. 102, 090401 (2009). - Host: Robert McDermott
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- TeV Gamma-Ray Astronomy with Milagro and HAWC
- Time: 4:00 pm
- Place: 4274 Chamberlin
- Speaker: Andrew Smith, University of Maryland, College Park
- Abstract: Milagro was a water Cherenkov detector that continuously viewed<br>
the entire overhead sky. The large field-of-view combined with<br>
the long observation time makes Milagro the most sensitive<br>
instrument available for surveys and especially for the study<br>
of large, low surface brightness sources. In this talk I will<br>
present recent results from Milagro including the identification<br>
of several new TeV sources associated with Fermi BSL (bright<br>
source list) objects within the Galactic plane. The success of<br>
Milagro has lead to the proposed High Altitude Water Cherenkov<br>
(HAWC) Observatory. HAWC will be built at a high altitude site<br>
(4100m a.s.l.) in central Mexico. The increased elevation, along<br>
with the re-optimization of the design will lead to a 15x<br>
sensitivity improvement compared to Milagro. - Host: Stefan Westerhoff
- Introductory Graduate Seminar
- High Energy Experimental
- Time: 5:30 pm
- Place: 2223 Chamberlin Hall
- Speaker: Carlsmith, Dasu, Heeger, Herndon, Mellado, Pan, Pondrom, Smith, Wu, University of Wisconsin Department of Physics