Unless otherwise noted, all physics seminars and colloquia are held on Tuesdays from 4:45 to 6:00 pm, in Lecture Room 3 of Merrill Science Center. Tea and snacks will be served before seminars at 4:15 in 204 Merrill. If you would like to be mailed seminar announcements, please send an email to Physics.
Contact colloquium organizer Larry Hunter with any questions about colloquia.
Tue, Sep 13, 2016
Tue, Sep 20, 2016
"Particle Astrophysics in a Can: The ADMX-HF Project"
Axions are hypothetical particles that were introduced into the standard model of elementary particle physics to solve the so-called "strong CP problem." Axions were subsequently (in the 1980's) theoretically identified as a possible dark matter candidate however the notion has been largely ignored with the exception of a single long running experiment, ADMX (for Axion Dark Matter Experiment). Failure to find a crisp supersymmetry signature with recent LHC experiments together with the diminishing parameter space from directed exotic heavy particle dark matter searches have reignited interest in the axion solution. A brief review of the background physics will be presented together with a update on the progress on the construction of a second higher mass range experiment, the Axion Dark Matter eXperiment at High Frequency (ADMX-HF), being assembled at Yale's Wright Nuclear Structure Laboratory. Results from the first three month production run will be presented.
Tue, Sep 27, 2016
"Quantum Hybrid Systems"
Semiconductor nanostructure devices for quantum information applications
The electron spin is a natural choice for encoding a quantum bit (qubit), the fundamental building block of a quantum information processor. In this talk I will review semiconductor quantum dot approaches to realizing spin qubits, and some of the key challenges to scaling up. I will describe recent efforts in my research group to develop CMOS-like silicon quantum dots for scalable, long-lived spin qubits, and ideas for implementing active error correction in such devices. Results will also be presented from experiments on quantum devices based on III-V nanowires, including superconductor-semiconductor junctions that show unusual effects such as Andreev bound states and proximity supercurrent. These nanowire junction devices are useful in the exploration of Majorana bound state physics as a possible basis for topological quantum computing.
Tue, Oct 4, 2016
Tue, Oct 18, 2016
Tue, Oct 25, 2016
Tue, Nov 1, 2016
Tue, Nov 8, 2016
"Quantum effects in the motion of a millimeter-scale object"
In 1909 Albert Einstein showed that the form of the Planck blackbody
spectrum implies that the radiation pressure exerted on a macroscopic
solid object is comprised of small (but not infinitesimal) kicks. Since
then, the notion of radiation pressure exerted by individual photons has
played an important role in developing our understanding of quantum
measurements. Recently, advances in optical and mechanical
instrumentation have highlighted the possibility of using the quantum
aspects of radiation pressure to detect quantum features in the motion
of macroscopic objects. In this talk I will describe our group's work in
this area, and will focus on recent measurements of the quantum motion
of a 40 nanogram oscillator that has been laser cooled nearly to its
Tue, Nov 15, 2016
Tue, Nov 29, 2016
Tue, Dec 6, 2016
Tue, Jan 24, 2017
"Generating and Controlling Ultrafast Electron Pulses for Time-resolved Electron Diffraction"
Ultrafast electron diffraction (UED) is a powerful technique that lets us measure the positions of atoms in a crystal as they evolve during chemical and physical transformations. These measurements can give insight into how materials work on a microscopic level as well as guide the design of devices that respond on fast timescales. For some time, the best-available time resolution in UED has hovered around 100 fs (1 fs =10^-15 s), just shy of the 10 fs resolution required to see the fastest atomic motions. In my talk, I’ll explain how ultrafast electron diffraction works and why it’s challenging to break the 100-fs resolution barrier. I’ll show experimental results on a new technique that uses terahertz electromagnetic fields to compress electron pulses in time. This technique has the potential to improve the resolution of UED below 100 fs and maybe even below ~1 fs, into the regime of electronic dynamics. The talk will also introduce ultrafast electron sources based on laser-triggered electron emission from nanometrically sharp metal tips. Not only is the physics of ultrafast electron emission in this system very rich, but the extraordinarily small source size in comparison with typical ultrafast flat photocathode sources can dramatically improve the beam quality, leading to smaller probe sizes, higher quality diffraction patterns, and enabling new techniques like ultrafast electron holography.
Tue, Jan 31, 2017
Tue, Feb 7, 2017
Tue, Feb 14, 2017
Tue, Feb 21, 2017
Tue, Feb 28, 2017
Tue, Mar 7, 2017
Tue, Mar 21, 2017
"Planet Formation through Radio Eyes."
The disks of gas and dust around young stars provide the raw material and initial conditions for planet formation. Millimeter-wavelength interferometry is a powerful tool for studying gas and dust in planet-forming regions, and it has recently undergone an immense leap in sophistication with the advent of the ALMA interferometer. I will discuss some ways in which millimeter-wavelength interferometry is being used to study the process of planet formation in circumstellar disks, with particular emphasis on the degree to which debris disk structure reflects the dynamics of embedded planetary systems.