Events at Physics
Events on Friday, November 6th, 2015
- R. G. Herb Condensed Matter Seminar
- Meissner qubit - characterization and vortex-probing applications
- Time: 11:00 am
- Place: 5310 Chamberlin Hall
- Speaker: Jaseung Ku , University of Illinois- Urbana Champaign
- Abstract: I will present a new type of transmon split-junction qubit which can be tuned by Meissner screening currents in the adjacent superconducting film electrodes. The best detected relaxation time (T1) was of the order of 50 us and the dephasing time (T2) about 40 us. The achieved period of oscillation with magnetic field was much smaller than in usual SQUID-based transmon qubits, thus a strong effective field amplification has been realized. This Meissner qubit allows an efficient coupling to superconducting vortices. I will present a quantitative analysis of the radiation-free energy relaxation in qubits coupled to Abrikosov vortices. The observation of coherent quantum oscillations provides evidence that vortices can exist in coherent quantum superpositions of different position states. According to our suggested model, the wave function collapse is defined by Caldeira-Leggett dissipation associated with viscous motion of the vortex cores.
- Host: McDermott
- Physics Department Colloquium
- Plasma kinetics in the inner heliosphere and the NASA Solar Probe Plus mission
- Time: 3:30 pm
- Place: Chamberlin 2241 (Coffee & Cookies at 3:15pm)
- Speaker: Stuart D. Bale, UC Berkeley
- Abstract: I will describe measurements of the electron velocity distribution function in the solar wind at 1 AU using the 3DP instrument on NASA's WIND spacecraft. Three distinct populations of electrons are observed and the collisional coupling between the cool, dense 'core' electron population and the solar wind protons can be observed directly. This Coulomb coupling relationship can be used probe the electron distribution of the solar corona and suggests that the coronal electron population will be highly nonthermal. I will also describe the NASA Solar Probe Plus mission, which will launch in 2018 and orbit the Sun with a final perihelion altitude of 9.8 solar radii, well within the predicted Alfven surface. Solar Probe Plus will make the first ever in situ measurements of plasma heating processes in the solar corona.
- Host: Forest