Loss Dependence on Geometry and Applied Power in Superconducting Coplanar Resonators

The loss in superconducting microwave resonators at low-photon number and low temperatures is not well understood but has implications for achievable coherence times in superconducting qubits. We have fabricated single-layer resonators with a high quality factor by patterning a superconducting aluminum film on a sapphire substrate. Four resonator geometries were studied with resonant frequencies ranging from 5 to 7 GHz: a quasi-lumped element resonator, a coplanar strip waveguide resonator, and two hybrid designs that contain both a coplanar strip and a quasi-lumped element. Transmitted power measurements were taken at 30 mK as a function of frequency and probe power. We find that the resonator loss, expressed as the inverse of the internal quality factor, decreases slowly over four decades of photon number in a manner not merely explained by loss from a conventional uniform spatial distribution of two-level systems in an oxide layer on the superconducting surfaces of the resonator.Comment: 4 pages, 5 figures, Submitted to ASC 2010 conference proceeding

Boosting fluxons for ballistic-logic power using an Aharonov-Casher ring

Superconducting logic is fast and energy-efficient relative to CMOS, but also fundamental studies are needed to scale up circuits for greater utility. Recently, ballistic shift registers for single-flux quanta (SFQ) bits were shown in simulation to allow high-efficiency superconducting gates. However, these gates are unpowered such that the bits slow after each gate operation and only a short sequence of gates is possible without added power. Here we show that a circuit based on an Aharonov-Casher ring can power these shift registers by boosting the bit velocity to a constant value, despite their unusual bit states constituted by two polarities of SFQ. As a step in its operation, each bit state is forced into a different ring arm and then accelerated. The circuit dynamics depend on various circuit parameters and choices of how to merge the bit-state paths. One design from each merge design choice is proposed to enable scaling up to an array of gates by adding serial biasing in a relatively simple way. We find adequate performance for ballistic logic in terms of boosted velocity, energy efficiency, and parameter margins. We also discuss the circuit's classical barriers; in a different regime this relates to the Aharonov-Casher effect.Comment: 17 pages, 10 figures, 1 tabl

Content and Correlational Analysis of a Corpus of MTV-Promoted Music Videos Aired Between 1990 and 1999

From 1990 to 1999 MTV promoted a series of 288 music videos called “Buzz Clips”, designed to highlight emerging artists and genres. Such promotion had a measurable impact on an artists’ earnings and record sales. To date, the kinds of musical and visual practices MTV promoted have not been quantitatively analyzed. Just what made some videos Buzzworthy, and others not? We applied two phases of content analysis to this corpus to determine the most common sonic and visual signifiers in Buzz Clips, then processed the results of that content analysis using polychoric correlations. Our findings show high degrees of shared variance between certain pairs of musical and visual elements observed in the sample music videos. We interpret a number of these relationships in terms of their relevance to a performer’s perceived ethnicity and gender, showing how certain audiovisual features regularly accompany white men (e.g., electric guitar) while others regularly accompany women and performers of color (e.g. drum machines)

Content and Correlational Analysis of a Corpus of MTV-Promoted Music Videos Aired Between 1990 and 1999

From 1990 to 1999 MTV promoted a series of 288 music videos called “Buzz Clips”, designed to highlight emerging artists and genres. Such promotion had a measurable impact on an artists’ earnings and record sales. To date, the kinds of musical and visual practices MTV promoted have not been quantitatively analyzed. Just what made some videos Buzzworthy, and others not? We applied two phases of content analysis to this corpus to determine the most common sonic and visual signifiers in Buzz Clips, then processed the results of that content analysis using polychoric correlations. Our findings show high degrees of shared variance between certain pairs of musical and visual elements observed in the sample music videos. We interpret a number of these relationships in terms of their relevance to a performer’s perceived ethnicity and gender, showing how certain audiovisual features regularly accompany white men (e.g., electric guitar) while others regularly accompany women and performers of color (e.g. drum machines)

Beyond the University: An Initiative for Continuing Engagement among Alumni

In an effort to leverage students’ positive community engagement experiences as they transition to and become alumni, Portland State University (PSU) embarked on a pilot “Continuing Engagement Program.” This article provides a rationale for this effort, an overview of the programmatic elements, lessons learned, and future engagement strategies. The authors situate the Community Engagement Program (CEP) in the current alumni engagement literature, share findings from the PSU program, and hope to inspire additional creative thinking and action to support alumni and other community members’ persistent engagement for positive community change