Colloquia & Seminars
  • JQI Seminar
    Speaker: Konrad Lehnert

    Title: Arbitrary temporal and spectral mode conversion of microwave signals with a mechanical oscillator

    Abstract: Electromagnetic waves provide a powerful way to link distant objects. They travel fast, interact weakly, and can be efficiently routed between locations using cables or fibers. These qualities make them ideal candidates for transmitting information in a quantum network. Yet linking quantum enabled devices with cables has proved difficult because most cavity quantum electrodynamics (cQED) systems used in quantum information processing can only absorb and emit signals with a specific frequency and temporal envelope. In this talk, I will describe a new type of tunable electromechanical device that overcomes both of these mismatches for microwave signals. In particular, I will show that it can alter the temporal and spectral content of microwave signals with noise sufficiently low to preserve quantum information. This device offers a way to build quantum microwave networks using separate and otherwise incompatible components.
    When: Mon, March 30, 2015 - 11:00am
    Where: CSS 2400
  • EPT Joint Seminar w/ Hopkins
    Joint Particle theory-experiment Maryland-Hopkins Seminar

    Seminar will be preceded by lunch at 12:30 pm. The talk is from 2:00 to 3:00 pm.

    Title: The LHC and the Search for New Physics

    Speaker: Albert de Roeck, CERN

    Abstract: The experiments at the LHC have completed data taking of proton-proton
    collisions at a centre of mass energy of 8 TeV in 2013. In the spring of this year
    the LHC will start its operation again at a higher centre of mass energy of
    13 TeV. We will review here a number of searches conducted with the present
    LHC data, leading so far to limits for possible New Physics, and discuss the
    prospects for the upcoming higher energy run. Eg. for the case of
    supersymmetry, with the first year of data taken at 13 TeV most of the
    limits derived from the 8 TeV data will be surpassed, making early
    discoveries possible. We will also pay special attention to the potential of
    the LHC data to contribute to the question of the nature of dark matter.
    When: Mon, March 30, 2015 - 12:30pm
    Where: PSC 3150
  • Condensed Matter Seminar
    Speaker Name: Tom Angelini

    Speaker Institution : University of Florida

    Title: TBA


    When: Mon, March 30, 2015 - 4:00pm
    Where: 0112 Chemistry Building
  • Space and Cosmic Ray Physics Seminar
    Speaker Name: Prof. Merav Opher

    Speaker Institution: Boston University

    Title: MAGNETIZED JETS DRIVEN BY THE SUN: THE STRUCTURE OF THE HELIOSPHERE REVISITED

    Abstract : The classic accepted view of the heliosphere is a quiescent, comet-like shape aligned in the direction of the Sun’s travel through the interstellar medium (ISM) extending for thousands of astronomical units (AUs). Here, we show, based on magnetohydrodynamic (MHD) simulations, that the tension (hoop) force of the twisted magnetic field of the Sun confines the solar wind plasma beyond the termination shock and drives jets to the north and south very much like astrophysical jets. These jets are deflected into the tail region by the motion of the Sun through the ISM similar to bent galactic jets moving through the intergalactic medium. The interstellar wind blows the two jets into the tail but is not strong enough to force the lobes into a single comet-like tail, as happens to some astrophysical jets. Instead, the interstellar wind flows around the heliosphere and into the equatorial region between the two jets. As in some astrophysical jets that are kink unstable, we show here that the heliospheric jets are turbulent (due to large-scale MHD instabilities and reconnection) and strongly mix the solar wind with the ISM beyond 400 AU. The resulting turbulence has important implications for particle acceleration in the heliosphere. The two-lobe structure is consistent with the energetic neutral atom (ENA) images of the heliotail from IBEX where two lobes are visible in the north and south and the suggestion from the Cassini ENAs that the heliosphere is “tailless.”

    Notes: Coffee, Tea & Cookies 4:15-4:30 PM
    When: Mon, March 30, 2015 - 4:30pm
    Where: Computer & Space Science Building, Room 2400
  • JQI Special Seminar
    Speaker: Anja Metelmann, McGill University

    Title: Nonreciprocal photon transmission and amplification via reservoir engineering

    Abstract: The general desire to break reciprocity in engineered photonic structures has garnered an immense amount of recent interest. For example nonreciprocal microwave-frequency devices are crucial to efforts at quantum-information processing with superconducting circuits. We discuss a general method for constructing nonreciprocal, cavity-based photonic devices, based on matching a given coherent interaction with its corresponding dissipative counterpart; it generalizes the basic structure used in the theory of cascaded quantum systems. In contrast to interference-based schemes, our approach allows directional behaviour over a wide bandwidth. We show how it can be used to devise isolators and directional, quantum-limited amplifiers; of particular interest is a directional phase-sensitive amplifier which is not limited by any fundamental gain-bandwidth constraint. Our approach is particularly well-suited to implementations using superconducting microwave circuits.
    When: Tue, March 31, 2015 - 11:00am
    Where: CSS 2115
  • Informal Statistical Physics Seminar
    Speaker Name: Zhixin Lu

    Speaker Institution : UMCP

    Title : Can Topologically Forbidden Interchange of Energy Surfaces Occur Under Slow Variation of a Hamiltonian?

    Abstract : I will talk about a particular type of one-degree-of-freedom, slowly changing, temporally periodic Hamiltonian system whose numerical simulation shows an apparent paradox. Specifically, we sprinkle many initial conditions (particles) on two constant energy phase space curves H=EA and H=EB. The H=EA curve encircles the H=EB curve. We then numerically follow their orbits forward in time by one cycle period. With large enough cycle period, at the end of the cycle, points initially on the curves H=EA and H=EB now appear to lie on two new constant energy curves H=EA′ and H=EB′ where the H=EB′ encircles the H=EA′ curve (as opposed to the initial case where the H=EA curve encircles the H=EB curve). Due to the uniqueness of the Hamiltonian dynamics, however, curves evolved under the dynamics cannot cross each other. This apparent paradox is resolved and its consequence is studied. I will also talk about how a very tiny amount of friction can have a major consequence, as well as what happens when a very large number of cycles is followed. I will also discuss how this phenomenon might extend to chaotic motion in higher dimensional Hamiltonian systems.
    When: Tue, March 31, 2015 - 1:15pm
    Where: Room 1116, IPST Building, Bldg 85
  • Physics Colloquium - Konrad Lehnert
    Speaker Name: Konrad Lehnert

    Speaker Institution: JILA, Boulder Colorado

    Title: Micromechanics: a new quantum technology

    Abstract: 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.

    hosted by Vlad Manucharyan
    When: Tue, March 31, 2015 - 4:00pm
    Where: PSC Lobby
  • Plasma Physics Seminar
    Speaker Name: Prof. Dennis Whyte

    Speaker Institution : Massachusetts Institute of Technology

    Title: Smaller & Sooner: Exploiting new technologies to accelerate fusion’s development

    Abstract: A new generation of superconducting (SC) tapes puts within reach loss-free magnetic fields with B > 20 Tesla on coil, doubling the field allowed by the present SC technology. The tapes can also provide demountable SC toroidal field coils. The ARC FNSF/Pilot design study explores how access to such technology would be a “game-changer” for small, robust tokamak reactors. The B3-4 dependence in critical fusion parameters allow both high energy gain and power density in much smaller devices, ~ 10x smaller than ITER in volume, while producing fusion energy ~500 MW and net electricity: features all highly attractive for the development of fusion energy. ARC operates far from all disruptive kink, pressure, density and shaping limits. In additions excellent access to robust steady-state (SS) scenarios is afforded by high-field, compact tokamaks. It is shown through simple 1-D analysis and the introduction of new dimensionless figures of merit that robust SS must arise from the combination of high-field and associated improvements in current drive at high B, particularly using integrated high-field Lower Hybrid launchers. A strong synergy exists between the high-B and demountable coils, allowing for simplified and improved fusion engineering choices: immersion liquid blankets, single-phase high temperature cooling, and a modular vacuum vessel, which becomes the only replacement item in the reactor, greatly reducing solid waste. The potential wins of high-field SC are so attractive that they should be pursued for magnetic fusion’s development.

    When: Wed, April 1, 2015 - 4:00pm
    Where: ERF 1207, Large Conference Room
  • High Energy Physics Seminar
    Speaker Name: Jacques Farine

    Speaker Institution : Laurentian University

    Title : "High Sensitivity Radon Measurements for Low Background Experiments"

    Abstract : The Sudbury Neutrino Observatory (SNO) has resolved the Solar Neutrino Problem by demonstrating the oscillation of solar neutrinos.
    This result was possible thanks to novel background monitoring techniques, including the assay of radium isotopes in ultra-pure water
    with a sensitivity of 1 atom/10 tonnes in the Thorium chain. The radon detectors developed to measure the radon emanation of the extracted radium will be
    presented, and the interpretation of counting results for inclusion in the physics signal extraction will be discussed. The counters’ sensitivity has been improved for the materials screening program of EXO-200, which measured directly the slowest process known in nature, the two-neutrino double-beta decay of 136-Xenon.
    The high sensitivity to the isotopes 222Rn, 220Rn and 219Rn has been of interest to other experiments. Further improvements are in progress in support
    of the radioactivity control program of nEXO.
    When: Wed, April 1, 2015 - 4:00pm
    Where: PSC 3150
  • Applied Dynamics Seminar
    Speaker Name: James Alexander

    Speaker Institution : University of Maryland

    Title: Dynamics of Langmuir films: theory and experiment

    Abstract : A Langmuir film is a molecularly thin film on a surface. Here we consider the behavior of such films on a flat water surface. (Note: “we” consists of a team of mathematicians, a physicist, a chemical engineer, and several students/post-docs.) The equilibrium state of a finite domain (= “blob”) of such a film is a circular disk. We consider the dynamical behavior when such a domain is disturbed. The tension at the boundary of the domain is the restoring force (so-called line tension, analogous to surface tension of a fluid), which competes against the viscosity of the underlying fluid. A prominent problem is to measure the line tension. The system is modeled as two coupled Navier-Stokes systems, which, because the Reynolds numbers are small, reduces to two coupled Euler flows. Solutions are found which permit comparison with experiment. An advance we make is to model the system globally, not just asymptotically at the end of relaxation to equilibrium. This requires advances in numerical techniques to make the computation effective. In this lecture, we describe the project, from conceptual beginning through to the quantitative dovetailing of theory with experiment.
    When: Thu, April 2, 2015 - 12:30pm
    Where: IREAP Large Conference Room, ERF 1207
  • Refreshments for CNAM Colloquium

    When: Thu, April 2, 2015 - 1:30pm
    Where: The "new" Toll Room, Phys. Rm 1305F
  • JQI Special Seminar
    Speaker: Alexander D. Cronin, University of Arizona

    Title: Atom interferometer gyroscope with spin-dependent phase shifts induced by light near a tune-out wavelength

    Abstract: Tune-out wavelengths measured with an atom interferometer are sensitive to laboratory rotation rates because of the Sagnac effect, vector polarizability, and dispersion compensation. We observed shifts in measured tune-out wavelengths as large as 213 pm with a potassium atom beam interferometer, and we explore how these shifts can be used for an atom interferometer gyroscope. For further information, see http://j.mp/TUNEOUT
    When: Thu, April 2, 2015 - 2:00pm
    Where: PSC 2136
  • CNAM Cond. Matter Colloquium
    Speaker: Dr. Vivien Zapf, Los Alamos National Laboratory

    TITLE: Hard and multiferroic magnetism in a frustrated antiferromagnet family

    ABSTRACT: I will discuss unusual hysteretic magnetic behavior and its coupling to ferroelectricity in a family of frustrated triangular magnets. In Sr3NiIrO6, we find a record high coercive magnetic field of 55 Tesla. This serves as an example of how the anisotropy of iridates that has been studied at a local level can affect bulk magnetism. Iridates have been a recent focus area of condensed matter research due to their unusual local magnetic configurations involving competing energy scales for crystal electric fields, spin-orbit coupling and exchange. In this material, 3d Ni2+ and 5d Ir4+ spins in oxygen cages alternate along chains, which in turn are arranged in triangular configurations that can be understood in the framework of a partially disordered antiferromagnetic model.

    In other (non-iridate) members of this family we also observe coupling of magnetic hysteresis to electric polarization. The ability of a magnetic order, and not just its domains, to evolve hysteretically around a magnetic hysteresis loop creates a coupled magnetic and electric hysteresis on a microscopic level.
    When: Thu, April 2, 2015 - 2:00pm
    Where: Phys Rm 1201
  • LPS Seminar
    Speaker Name: Dr. David A. Hammer

    Speaker Institution : Cornell University

    Title : Fusion Power, a Grand Challenge Applied Science and Engineering Problem for the 21st Century

    Abstract : Although "everyone knows" that we will always have fusion 20 years from now, no matter what the year is today, there has been considerable progress in the 60 years since the quest for practical controlled fusion power began. In this talk, I will discuss the fundamentals of generating energy from fusion of hydrogen nuclei, what reaction look most promising for a first generation reactor, the benefits of working even harder to achieve a second generation reactor, and why we want to do it (no matter how long it takes to succeed). I will then talk about where we are on the road to a practical fusion reactor of some sort and what major technological achievements are still needed to get there.

    Notes: LPS is located at 8050 Greenmead Drive in College Park. There is parking at LPS and overflow parking at the adjacent LTS building but not at the 4H building. LPS is on the UMCP shuttle route; take #105 for the Courtyard Apts. Please use the phone on the left hand side of the front door to call the receptionist for entry.


    When: Thu, April 2, 2015 - 3:30pm
    Where: Laboratory for Physical Sciences, 8050 Greenmead Drive, College Park, MD 20740, United States
  • MCFP Colloquium
    Speaker Name: S. James Gates, Jr.

    Speaker Institution: University of Maryland

    Title: Think Different: Applying the Old MacIntosh Mantra
    to the Representation Theory of Supersymmetry

    Abstract: The conventional and traditional ways of investigating the
    representation theory of supersymmetry have been within
    the confines of relativistic quantum theories of fields and
    strings. This presentation discusses an array of new tools
    that have been proposed in the effort to create a more
    complete foundation.
    When: Thu, April 2, 2015 - 4:00pm
    Where: PSC 3150
  • JSI Mini-Symposium
    JSI Mini-Symposium -- April 3, 2015

    "Energetic Particles"
    Schedule at http://jsi.astro.umd.edu/upcoming-mini-symposium

    Date: Friday, April 3, 2015
    Time: 12:30 PM - 5:30 PM (Lunch available beginning at 11:30 am in the ellipse area outside of PSC 1136)
    Location: Room 1136 Physical Sciences Complex, University of Maryland, College Park
    When: Fri, April 3, 2015 - 12:30pm
    Where: PSC 1136
  • Materials Science and Engineering Seminar
    Speaker Name: Darrell G. Schlom

    Speaker Institution : Cornell University

    Title : Thin-Film Alchemy: Using Strain and Dimensionality to Unleash the Hidden Properties of Oxides

    Abstract : Guided by theory, unparalleled properties—those of hidden ground states—are being unleashed by exploiting large strains in concert with the ability to precisely control dimensionality in epitaxial oxide heterostructures. For example, materials that are not ferroelectric or ferromagnetic in their unstrained state can be transmuted into ferroelectrics, ferromagnets, or materials that are both at the same time. Similarly, new tunable dielectrics with unparalleled performance have been created. Results of fundamental scientific importance as well as revealing the tremendous potential of utilizing multicomponent oxide thin films to create devices with enhanced performance will be shown.
    When: Fri, April 3, 2015 - 1:00pm
    Where: Room 2108 Chemical & Nuclear Engineering Building
  • JQI Seminar
    Speaker: Ileana Rau, IBM Research, San Jose, CA

    Title: Toward Single Atom Magnets

    Abstract: Magnetic anisotropy is a fundamental property of magnetic materials that governs the stability and directionality of their magnetization. The ability to control the magnetic anisotropy of nanoscale systems will open novel avenues for spintronics, magnetic memory devices, and quantum computation. At the atomic level, magnetic anisotropy originates from the spin-orbit coupling that connects the spin moment of a magnetic atom to the spatial symmetry of its ligand or crystal field environment. In the case of 3d transition metal atoms, the same crystal field that is necessary for the anisotropy usually quenches the orbital moment and reduces the total magnetic moment of the atom to its spin component. As a result, single molecule magnets and magnetic tunnel junctions show an anisotropy energy per atom that is typically one to two orders of magnitude smaller than the maximal value allowed by the spin-orbit coupling. We have overcome this limitation by carefully designing the coordination geometry of magnetic atoms on a surface to preserve the orbital moment while inducing uniaxial anisotropy. I will present scanning tunneling spectroscopy and x-ray absorption spectroscopy measurements that show that single Cobalt atoms deposited on a thin MgO layer retain most of their free-atom orbital moment L=3. Because Cobalt adsorbs on top of the Oxygen atom, the resulting crystal field is effectively cylindrical and leads to a strikingly large magnetic anisotropy energy, at the theoretical limit. Spin-polarized tunneling measurements reveal a stable magnetic groundstate with a large total moment of ~5.5µB and a long-lived excited state of opposite magnetic moment with a relaxation time of 0.2 ms. These results offer a strategy,
    based on symmetry arguments and careful tailoring of the interaction with the environment
    for the rational design of nanoscopic permanent magnets and single atom magnets.
    When: Mon, April 6, 2015 - 11:00am
    Where: CSS 2400
  • Biophysics
    Speaker Name: Kimberly Stoka

    Speaker Institution : University of Maryland

    Title : Joining Forces with Biology: Bioengineering Perspectives on Tumor Cell Migration

    Abstract : Cell homeostasis and diverse processes, including migration, are tightly regulated by cell volume. In vivo, metastatic tumor cells must navigate complex, heterogeneous microenvironments when migrating through tissues, including longitudinal tracks formed by anatomic structures. Intriguingly, we have discovered that the classical model of cell migration on two-dimensional substrates (relying on actin polymerization, cell adhesion to the substrate, and myosin II-mediated contractility) does not apply to metastatic tumor cells migrating through three-dimensional confined spaces. We therefore hypothesized that an alternate mechanism based on cell volume regulation via ion channels and aquaporins drives cell migration in these confined microenvironments, where cells must deform in order to squeeze through physically restrictive spaces. Using a multidisciplinary approach that integrates microfabrication techniques, molecular biology, live cell imaging, and theoretical modeling based on physics, we have developed an “Osmotic Engine Model” of cell migration, which demonstrates that osmotically-driven water flow regulates cell migration in confined microenvironments. Importantly, our theoretical model predicts many key non-intuitive experimental results. Collectively, this study represents a new paradigm for cell migration in confined microenvironments and elucidates ion pumps and aquaporins as new molecular targets that may be exploited for future development of cancer therapeutics.
    When: Mon, April 6, 2015 - 4:00pm
    Where: 0112 Chemistry Building
  • JSI Colloquium
    Refreshments available at 3:30 pm

    Speaker: Jonathan McKinney

    Speaker Institution: UMD

    Title: Growing Black Holes via Super-Eddington Accretion

    Abstract: Black hole engines power phenomena from the large-scale heating of gas in galaxies and clusters down to the event horizon-scale formation of relativistic jets. We reveal how our unique state-of-the-art general relativistic radiation magnetohydrodynamical simulations of accreting black holes and their feedback (as radiation, winds, and jets) could help solve the problem of the rapid formation of high redshift quasars and might explain the origin of the black-hole-mass to bulge-velocity-dispersion (M-sigma) correlation in galaxies. Radiation physics in simulations will provide a fresh understanding of a broad range of phenomena including active galactic nuclei, x-ray binaries, gamma-ray bursts, tidal disruption events, and strong gravity regimes like those probed by the Event Horizon Telescope.

    https://jsi.astro.umd.edu/jsi-colloquium-series
    When: Mon, April 6, 2015 - 4:00pm
    Where: PSC 1136
 

Department of Physics


University of Maryland
College Park, MD 20742-4111
Phone: 301.405.3401
Fax: 301.314.9525