Events at Physics
Events on Tuesday, April 19th, 2016
- R. G. Herb Condensed Matter Seminar
- Semiconductors for Superconducting Qubits
- Time: 10:00 am
- Place: 5310 Chamberlin Hall
- Speaker: Karl Petersson, University of Copenhagen
- Abstract: We have developed a superconducting transmon qubit with a semiconductor-based Josephson junction element [1,2]. The junction is made from an InAs nanowire with in situ molecular beam epitaxy-grown superconducting Al contacts. This gate-controlled transmon, or gatemon, allows simple tuning of the qubit transition frequency using a gate voltage to vary the density of carriers in the semiconductor region. In the first generations of devices we have measured coherence times up to 10 µs. These coherence times, combined with stable qubit operation, permit single qubit rotations with fidelities of ~99.5% for all gates including voltage-controlled Z rotations. Towards multi-qubit operation we have also implemented a two qubit voltage-controlled cPhase gate. In contrast to flux-tuned transmons, voltage-tunable gatemons may simplify the task of scaling to multi-qubit circuits and enable new means of control for many qubit architectures.
 T. W. Larsen et al., Phys. Rev. Lett. 115, 127001 (2015).
 G. de Lange et al., Phys. Rev. Lett. 115, 127002 (2015).
- Host: Smith/Coppersmith
- Astronomy Colloquium
- TUESDAY TALK
- A Philosophically-Informed Appraisal of the Schmidt-Sanduleak Law of Star Formation: "Not Even Wrong"
- Time: 12:00 pm - 1:00 pm
- Place: 4421 Sterling Hall
- Speaker: Barry F. Madore, Carnegie Observatories and Dept of Astronomy & Astrophysics University of Chicago
- Abstract: Galaxy evolution simulations depend critically upon modeling star
formation; however, astronomy does not yet have a "first principles"theory of star formation. One of the most influential parametric descriptions of star formation is the so-called "Schmidt Law", which supposes that the rate of star formation is properly described as a power-law function of the local gas density. I will discuss the popular appeal of the Schmidt Law among galaxy modelers, as well as its observational and conceptual support. But I will then step back and adopt a philosophically-informed stance and make the case that the rather uncritical acceptance of this "law" for more than half a century thwarted a more straightforward, and physically more meaningful interpretation of the empirical data that is now in hand. Viewed and interpreted in the context of cyclical autocatalytic)reaction network I will present new data and new conclusions on the rate of star formation in galaxies deriving explicitly the timescales involved in the cyclical process of star formation and the efficiencies involved in converting gas into stars.
- Host: Prof Jay Gallagher
- Chaos & Complex Systems Seminar
- Novel-writing as a way to organize data
- Time: 12:05 pm - 1:00 pm
- Place: 4274 Chamberlin Hall (refreshments will be served)
- Speaker: Russell Gardner, Jr., Freelance scholar
- Abstract: This is a follow-up presentation to a CCSS presentation, “Writing a Novel,” in September, 2014. This talk includes lessons learned from that first effort. I call myself a novelist not because I’ve published (yet), but because I have a daily routine of writing (it’s my occupation), have studied the process in readings and courses, and have presented ongoing work to others. The present twelve chapter first draft of a second novel, Different Windows, has been done independently, this time, of any formal class (although I employ a paid editor). Each chapter includes about 25-manuscript pages. I will focus on Novel-writing to organize data and its relations to other forms of scientific, and “ordinary,” means of human data-processing, Fiction as a way to talk publically and formally about matters that worry and interest me, namely, the climate crisis, billionaire denial of the crisis, especially highly influential ones who seek to minimize government in all its forms (Jane Mayer’s Dark Money (2016)), the fate of one’s descendents after one dies, the treatment form of psychoanalysis which has retreated from the forefront of thinking, but which needs representation in an understandable format, and some bleak optimism about a dismal seeming future. Formulations of Professor and Chairman of UW’s Department of English, Caroline Levine, who has written The Serious Pleasure of Suspense (2003). Process of working out a second draft of Different Windows and envisioned attempts to publish the completed work.
- Host: Clint Sprott
- Theory Seminar (High Energy/Cosmology)
- Evading non-linearities: Baryon Acoustic Oscillations at the linear point
- Time: 3:30 pm
- Place: 5280 Chamberlin Hall
- Speaker: Stefano Anselmi, Case Western Reserve University
- Abstract: Cosmology has made fundamental progress thanks to the role of standard rulers. The acoustic peak in the Large Scale Structure clustering correlation function is one of them. However, in the era of precision cosmology, its power has been highly challenged by how late time non-linearities distort the correlation function. Fortunately this is not the end of the story! I will explain how we can evade non-linearities identifying a scale in the correlation function, called the “linear point”, that is an excellent cosmological standard ruler: its position is insensitive to non-linear gravity, redshift space distortions, and scale-dependent bias at the 0.5% level; it is geometrical, i.e. independent of the power spectrum of the primordial density fluctuation parameters. Moreover, the linear point increases its appeal as it is easily identified irrespectively of how non-linearities distort the correlation function. Equally relevant, the correlation function amplitude at the linear point is similarly insensitive to non-linear corrections to within a few percent. Therefore, exploiting the particular Baryon features in the correlation function, we propose three new estimators for growth measurements. We perform a preliminary test in current data finding encouraging results and motivating more careful future investigations.
- Host: Amol Upadhye