Events at Physics
Events on Thursday, April 20th, 2017
- R. G. Herb Condensed Matter Seminar
- Entangling approaches for capacitively coupled semiconductor spin qubits
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Vanita Srinivasa, Sandia
- Abstract: Many proposed realizations of quantum information processing rely on rapid and robust entanglement of coherent qubits over a wide range of distances. While implementations based on electron spins in solids can take advantage of both the relative isolation of spin qubits from their environment and rapid control of the electron charge, entangling mechanisms in these systems are often limited in range and remain susceptible to charge-based decoherence. I will describe our theoretical approaches to addressing these challenges for spin qubits encoded in multiple electrons within systems of coupled quantum dots. We analyze a new regime for capacitive coupling of two-electron spin qubits that leads to high theoretical fidelities for entangling gates within silicon-based implementations in the presence of charge noise and relaxation. We also show that the three-electron resonant exchange qubit provides both a protected operating point for rapid single-qubit manipulation and an electric dipole moment that enables multiple approaches for long-range entangling gates via a superconducting microwave resonator. These methods are inspired by techniques from circuit quantum electrodynamics, Hartmann-Hahn double resonance in NMR, and the Cirac-Zoller gate for trapped ions.
- Host: Coppersmith
- Astronomy Colloquium
- Galaxy Transformations And The Quenching of Star Formation at High Redshift
- Time: 3:30 pm - 5:00 pm
- Place: 4421 Sterling Hall, Coffee and Cookies 3:30 PM, Talk at 3:45 PM
- Speaker: Mauro Giavalisco, University of Massachusetts
- Abstract: There is convincing evidence that massive galaxies (i.e. M~M*) undergo profound structural and morphological transformations as their star formation activity comes to a halt and they enter a phase of passive evolution. We do not yet understand which physical mechanism, or mechanisms, among a number of plausible ones, are responsible for the quenching. Nor do we understand what drives the morphological transformations. In this talk I will review some recent observations of both structural and morphological transformations and of quenching in galaxies at redshift 1<z<2.5, namely at the peak of the cosmic star formation activity, and discuss possible interpretations for the underlying physics of both. I will also present very recent observations that are informing us on the joint evolution of dark and baryon matter in galaxies and point to a possible common origin for both quenching and structural transformations. I will conclude by discussing some of the interpretations and by offering my speculations.
- Host: Astronomy Dept