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The Spring 2015 colloquia will be held in the lobby of the Physical Sciences Complex

Each week during the semester, the Department of Physics invites faculty, students and the local community to hear prominent scientists discuss intriguing physics research. The Spring 2015 colloquia will be held Tuesdays in the Physical Sciences Complex lobby at 4:00 p.m. (preceded by light refreshments at 3:30 p.m.)

Parking is available in the Regents Drive Parking Garage (PG2). An attendant will direct visitors within the garage. Additionally, a free ShuttleUM bus runs between the College Park Metro Station and Regents Drive at about eight-minute intervals.

For further information, please contact the Physics Department at 301-405-5946 or email This email address is being protected from spambots. You need JavaScript enabled to view it..

February 3
Elizabeth Hayes (NASA)

New Views of the Galaxy in Gamma Rays from the Fermi Gamma-ray Space

Over the past 6 years, NASA's Fermi Gamma-ray Space Telescope has revolutionized our view of the Milky Way. Fermi's Large Area Telescope (LAT) continues to deepen and sharpen our picture of the high energy sky from 100 MeV to > 300 GeV. Of the more than 3000 sources in the third LAT catalog, nearly 9% are associated with sources in our own Galaxy while many others remain to be associated. New classes of gamma-ray emitters have been discovered and previously known classes of emitters have been studied in fantastic detail. LAT data have revealed for the first time a large-scale feature of the Milky Way, dubbed the Fermi Bubbles. For much of the past year, Fermi employed a modified sky survey to gain additional exposure toward the Galactic Center and to shed light on the unexplained excess of gamma rays observed by LAT in that region and the possible interpretation as a dark matter signal. I'll give an overview of key results from the Fermi mission and its continued role in understanding energetic phenomena in our Galaxy.

February 10
John Carlstrom (University of Chicago)

Physics and Cosmology with the Cosmic Microwave Background

The study of the cosmic microwave background (CMB) has driven spectacular advances in our understanding of the origin, make up and evolution of our universe. We now have a standard cosmological model, LCDM, that fits all the cosmological data with only six parameters, although there are some tensions that may hint at that cracks in the model. Far from being the last word in cosmology, the model points to exciting times ahead using the CMB to explore new physics, i.e., inflation, dark matter, dark energy, neutrino masses and possible additional relativistic species, or dark radiation. This talk will review the current status and near term plans for CMB measurements, with emphasis on the South Pole Telescope, and discuss the plans for the next generation experimental program, CMB-S4.

Wed February 18
An Experiment
February 24
Andrew Childs (QuiCS/University of Maryland)

Quantum Algorithms for Simulating Quantum Mechanics

Simulating the dynamics of quantum systems is a major potential application of quantum computers. Quantum simulation can be applied to model chemical reactions and to predict the behavior of materials. It can also be used as a tool to develop other quantum algorithms. While it has long been known that quantum computers can efficiently simulate quantum dynamics, recent work has led to dramatically improved algorithms. In this talk, I will describe some of these advances, including a quantum algorithm with exponentially improved performance as a function of the allowed error.

March 3
Harry Weller (New Enterprise Associates)

Not All Those Who Wander Are Lost

An undergraduate degree in physics can lead to opportunities far removed from research in academia. My journey has been rich and varied. From the physics lab at Duke to piloting F-18s, deploying large software systems, to an MBA at Harvard and finally to the world of venture capital at the nation's largest firm; hopefully, I'll illustrate that not all wandering physics majors are lost...

March 10
Michael Brown (Swarthmore College)

A Career as a Physicist at a Liberal Arts College: A 20-year Retrospective

The goal of this talk is to give an overview of the benefits and demands of a career of a physicist at an undergraduate-only liberal arts college. The perspective will be from my 20 year career as a plasma physicist at Swarthmore College, while drawing on contacts and visits from many other liberal arts colleges around the country. A liberal arts college professor is both teacher and scientist, but always with an eye towards mentoring undergraduates. I'll draw on examples from my own research on plasma turbulence and reconnection on the SSX device, as well as 20 years of teaching at Swarthmore.

March 24
Peter Graham (Stanford University)

Axion Detection with NMR

The axion is a well-motivated dark matter candidate, but is challenging to detect. We propose a new way to search for axion dark matter, the Cosmic Axion Spin Precession Experiment (CASPEr). Nuclei that are interacting with axion dark matter acquire time-varying nuclear moments such as an electric dipole moment. Nuclear magnetic resonance techniques and high-precision magnetometry can be used to search for this signal. With current techniques, this experiment has sensitivity to axion masses below 10^-9 eV, corresponding to theoretically well-motivated axion decay constants around the grand unification and Planck scales. With improved magnetometry, this experiment could ultimately cover the entire range of masses below 10^-6 eV, just beyond the region accessible to current axion searches. A discovery in such an experiment would not only reveal the nature of dark matter and confirm the axion as the solution of the strong CP problem, but would also provide a glimpse of physics at the highest energy scales, far beyond what can be directly probed in the laboratory.

March 31
Konrad Lehnert (University of Colorado Boulder)

Micromechanics: a new quantum technology

In modern information technology, micromechanical oscillators are ubiquitous signal processing elements. Because the speed of sound is so slow compared to the speed of light, mechanical structures create superb compact filters and clocks. Moreover they convert force and acceleration signals into more easily processed electrical signals. Although these humble devices appear manifestly classical, they can exhibit quantum behavior when their vibrations are strongly coupled to optical light or to microwave electricity. I will describe our progress in using this recent and exciting result to develop quantum information processing elements or quantum enhanced sensors that exploit the unique properties of mechanical systems. In particular, we are developing a device that uses a mechanical oscillator to transfer information noiselessly between electrical and optical domains. In the quantum regime, this device would enable a communication network with information security guaranteed by physical laws of nature and information capacity that exceeds the classical "Shannon" bound.

April 7
Cancelled due to power outage
April 14

(in the Toll Physics Building Lecture Hall)

W.J. Carr Lecture - Carlo Beenakker (Leiden University)

Majorana Braiding in Superconductors: How to Operate on a Zen Particle

Among the many exotic properties of topological superconductors, the prediction that they can host Majoranas stands out both for its fundamental interest and for possible applications in topological quantum computing. To exchange (braid) pairs of Majoranas is the heroic experiment, since it would identify them as a fundamentally new type of quasiparticles with non-Abelian statistics. The road towards this goal has several milestones, starting from the detection of the zero-mode itself, on which the present generation of experiments is focused. In this talk we look ahead towards the next milestones: the construction of a qubit out of Majoranas, the measurement of its coherence times, and finally the braiding experiment to demonstrate its non-Abelian nature.
The key problem that we address is how to operate on a cipher with zero charge, zero spin, zero energy, and zero mass.

April 21
Bill Foster (U.S. House of Representatives)

What Life is Like as a Scientist in Congress

In this presentation, Congressman Bill Foster will share insight about life as a scientist in Congress. Bill began his career at the age of 19, when he and his younger brother co-founded Electronic Theatre Controls, Inc., a company that now manufactures over half of the theater lighting equipment in the United States. After receiving his Ph.D. in Physics at Harvard University, Bill spent over 20 years doing high-energy physics research at Fermi Lab. He is the co-inventor of the recycler ring, the latest of Fermi's giant particle accelerators, and was a member of the team that discovered the top quark. Bill began his political career in 2007 and will speak about his transition from science to Congress. He will also review the current status of federal support for scientific research and development and other key issues facing Congress today.

Thursday April 23
Ian Appelbaum, University of Maryland

Symmetry, Anisotropy and Dimensionality: Spin physics in the elemental semiconductors Si, Ge, and P

By the 1980s, an accumulation of decades of research on charge transport in the elemental semiconductors silicon and germanium led to a lingering perception that there was nothing left for condensed matter physics to do with them. However, just before arriving at UMD almost 7 years ago, my lab demonstrated that these "old dogs" could be taught a few more "new tricks": Basic research on charge dynamics in these electronic materials eventually led to scores of real-life device applications, but spin dynamics remained unexplored. We figured out how to overcome several experimental challenges to inject spin-polarized electrons into these otherwise-nonmagnetic materials, and detect their remaining non-equilibrium spin orientation after traveling over amazingly long distances. In this talk, I will describe some of our many recent breakthroughs enabled by unique experimental capabilities and thorough theoretical understanding of both intrinsic and extrinsic phenomena dominating spin transport in Si and Ge. Furthermore, these two examples are not the end of the story, as new research moves forward into the spin physics of 2D elemental semiconductors like single-layer black phosphorus, or 'phosphorene'.
April 28
Samir Kaul

Entrepreneurial Roller Coasters

May 5
Sam Krucker (University of California, Berkeley)

Hard X-ray Observations as Diagnostics of Particle Acceleration in Solar Flares

Solar flares are powered by an impulsive release of magnetic energy stored in the solar atmosphere. The release of magnetic energy is heating coronal plasma, but as much as half of the released energy goes into particle acceleration. The acceleration mechanisms that provide these efficient conversions of magnetic energy into supra-thermal particles are currently not well understood. In the past years however, significant progress has been made on the
observational side; thanks in particular to hard X-ray observations by Reuven Ramaty High Energy Spectroscopic Imager (RHESSI), a NASA small explorer mission. After an extensive introduction, I will review recent observational results obtained by RHESSI. Furthermore, I will briefly describe future instrumentation such as the hard X-ray instrument STIX on board ESA's Solar Orbiter mission and a sounding rocket experiment called FOXSI that successfully used hard X-ray focusing optics for solar observations.

May 12
Raymond Brock (Michigan State)

That Spin 0 Boson Changes Everything:The Future of the Energy Frontier in Particle Physics

The "Higgs Boson" discovery requires us to think differently about planning for the future of Particle Physics. While the decades-long confirmation of the Standard Model itself an historic episode, as a dynamical model of nature it is unhelpful as a clear guide to the future. I'll review the features of the Standard Model that make it superb, I'll point out why it's frustrating, and I'll describe the hints that motivate us in the coming decades.

Upcoming Events


Wed, Aug 5, 2015 1:00 pm - 2:30 pm


Wed, Aug 5, 2015 2:00 pm - 3:00 pm


Mon, Aug 10, 2015 11:00 am - 12:00 pm