Fall 2016 Colloquium Schedule

Colloquia are Wednesdays at 4:00 p.m. in DUAN G1B20, unless otherwise noted.

Coffee, tea and cookies will be available before regular colloquia beginning at 3:45 p.m. in DUAN G1B31.

August 24 — "NASA’s Juno Mission to Jupiter: What’s Inside the Giant Planet?"

• Presenter: Fran Bagenal, University of Colorado Boulder
• Host: Mihaly Horanyi
• Abstract: Jupiter is a planet of superlatives: the most massive planet in the solar system, rotates the fastest, has the strongest magnetic field, and has the most extensive satellite system of any planet. NASA’s Juno mission was launched in August 2011 and went into orbit over Jupiter’s poles on July 4th this summer.  Juno’s principal goal is to understand the origin and evolution of Jupiter. Underneath its dense cloud cover, Jupiter safeguards secrets to the fundamental processes and conditions that governed our solar system during its formation. As our primary example of a giant planet, Jupiter can also provide critical knowledge for understanding the planetary systems being discovered around other stars. With its suite of science instruments, Juno will investigate the existence of a solid planetary core, map Jupiter's intense magnetic field, measure the amount of water and ammonia in the deep atmosphere, and observe the planet's auroras. Juno will let us take a giant step forward in our understanding of how giant planets form and the role these titans played in putting together the rest of the solar system. In Greek and Roman mythology, Jupiter drew a veil of clouds around himself to hide his mischief. It was Jupiter’s wife, the goddess Juno, who was able to peer through the clouds and reveal Jupiter’s true nature.  Juno is also the first spacecraft to fly over Jupiter’s aurora and will measure both the energetic particles raining down on the planet and the bright “northern & southern lights” they excite.

August 31 — "Cosmic Dust Research at the Colorado Dust Accelerator"

• Presenter: Tobin Munsat, University of Colorado Boulder
• Host: John Price
• Abstract: Cosmic dust grains play a central role in astrophysics and planetary science; the interaction of dust grains with planetary surfaces and atmospheres can drive weathering processes, surface chemistry (for airless bodies), and even atmospheric chemistry on Earth. Dust-detecting instruments can provide insight into the environment where the particles were formed, whether that is the interstellar medium, comets, asteroids, or even ejected from the surfaces of planets and moons. From a basic physics point of view, hypervelocity impact experiments can access extremely high energy density levels. To address many facets of cosmic dust research in the lab, we have recently developed a dust accelerator on the east campus of CU. This is a 3 MV electrostatic linear accelerator which launches particles in the size range of 0.1 to a few micrometers and velocities up to 100 km/s onto a variety of targets. This talk will describe the basic details of the accelerator and provide an overview of several lines of research being carried out by our group.  Specifically, I will discuss hypervelocity impact cratering experiments in thin films, impact experiments into cryogenic (ice) targets, making "shooting stars" in the lab, and the local development of dust detector instruments that have flown to the moon and will soon fly to Jupiter's moon Europa.

September 7 — "The End of Inflation"

• 
  Presenter: Tom Giblin, Kenyon College
• Host: Ethan Neil
• Abstract: The evidence for a hot, dense, early stage of the Universe is overwhelming.  Setting up a Universe in this hot-dense stage is more of a challenge.  While Cosmic Inflation as a paradigm has been successful at negotiating  the issues of the Hot Big Bang, its conclusion is marked by a cold, empty state that needs to quickly and efficiently reheat.  Violent processes, turbulent phase transitions and non-linear processes characterize this period and might help us shed light on the particle physics of the very young, very energetic early Universe.  I will describe how we have been using large numerical simulations to calculate precision observables that will help to constrain the growing number of early universe scenarios.

September 14 — "Apples vs. Oranges: Comparison of Student Performance in a MOOC vs. a Brick-and-Mortar Course"

• Presenter: Michael Dubson, University of Colorado Boulder
• Host: John Price
• Abstract: In the fall of 2013, my colleagues and I taught the calculus-based introductory physics course to 800 tuition-paying students at the University of Colorado at Boulder. At the same time we taught a free massive open online course (MOOC ) version of the same course, through Coursera.com. The initial enrollment in the MOOC was 10,000 students, of whom 255 completed the course. Students in both courses received identical lectures with identical embedded clicker questions, identical homework assignments, and identical timed exams. We present data on participation rates and exam performance for the two groups. We find that the MOOC is like a drug targeted at a very specific population. When it works, it works well, but it works for very few students. This MOOC worked well for older, well-educated students, who already had a good understanding of Newtonian mechanics.

September 21 — "Tragic tale of the mathematical genius Ramanujan"

• Presenter: Ramamurti Shankar, Yale University
• Host: Rahul Nandkishore
• Abstract: In this talk I will describe the remarkable life and mathematics of Srinivasa Ramanujan (1887-1920), an unknown self-educated clerk from South India who stunned the world of western mathematics with his results on number theory, modular functions etc., that continue to challenge us till this day. I will describe his early life in India, his discovery by Cambridge mathematician G H Hardy, his few years in Cambridge and his untimely death at age 32.

September 28 — "Shared vibrations:  How photosynthetic light harvesting approaches 100% efficiency”

• Presenter: David Jonas, Department of Chemistry and Biochemistry, University of Colorado Boulder
• Host: John Price
• Abstract: Almost all life on earth depends on photosynthesis, and almost all the power our civilization uses has been stored as fuel by photosynthesis.  In photosynthesis, light is harvested by antenna proteins that can transfer the photon’s energy to a reaction center with near unit quantum efficiency.  The remarkable efficiency of these energy transfer processes has been a mystery for over 60 years and we cannot replicate it artificially.  Recent femtosecond two-dimensional (2D) spectroscopy experiments on antenna proteins found signatures initially attributed to electronic coherence that have sparked discussion about the role of quantum mechanics in biology; it is puzzling that these signatures persist for longer than the apparent energy transfer timescale.   We have recently shown that intramolecular vibrations shared across pigments can drive electronic energy transfer outside the Born-Oppenheimer picture of fast electrons and slow vibrations.  Such shared vibrations on the ground electronic state of the antenna generate all of the observed 2D signatures and their properties reveal the design principle for the antenna.  There are indications that this new mechanism may be operative in a variety of antenna proteins using 5 different photosynthetic pigments that are responsible for over half of the light harvesting on our planet.

**Special Colloquium/Nuclear Particle Physics Seminar** Monday, October 3 — "The Physics of Non-Hydrodynamic Modes"

• Presenter: Paul Romatschke, University of Colorado Boulder
• NOTE SPECIAL LOCATION: DUAN G125
• Abstract: Examples for hydrodynamic collective modes are sound waves, shear and diffusive modes. But what are non-hydrodynamic collective modes? Most physicists likely have never ever heard about non-hydrodynamic modes in their entire career. Indeed, there does not seem to be a single textbook on this topic. This colloquium will give an introduction to the physics of non-hydrodynamic modes, featuring gravitational waves, string theory predictions for experiment, the coolest and hottest stuff on earth and high-temperature superconductors.

October 5 — “A synthetic quantum magnet made of hundreds of trapped ions”

• Presenter: John Bollinger, NIST Boulder
• Host: Scott Diddams
• Abstract: Entanglement between individual quantum objects exponentially increases the complexity of quantum many-body systems, so systems with more than 30-40 quantum bits cannot be fully studied using conventional techniques and computers. To make progress at this frontier of physics, Feynman’s pioneering ideas of quantum computation and quantum simulation are now being pursued in a wide variety of well-controlled quantum platforms.  Trapped-ions are naturally suited for simulating quantum magnetism, and exhibit desirable properties such as high-fidelity state preparation and readout, and long trapping and coherence times.  I will discuss how variable range, quantum magnetic interactions can be engineered with trapped ions, focusing on our work with 2-dimensional arrays of several hundred ions crystallized in a Penning ion trap.  In particular, I will highlight our recent experiments that benchmark quantum dynamics and entanglement, and utilize our ability to time-reverse the dynamics to measure out-of-time-order correlation functions that quantify the spread of quantum information throughout the system.

October 12 — "On string theory, particle physics and cosmology"

• Presenter: Fernando Quevedo, Director - ICTP, Trieste and Cambridge University
• Host: Shanta de Alwis
• Abstract: An overview will be given for the recent developments in string theoretical scenarios to address particle physics and cosmology questions.

October 19 — "From BEC to CEO: the Entrepreneurial Experience"

• Presenter: Chris Myatt, CEO - MBio Diagnostics
• Host: Scott Diddams
• Abstract: Can academic training in physics – at CU, JILA, and at NIST – prepare you to start a company?  While the subject of your research may not be directly applicable to industrial problems—in my case, Bose-Einstein condensation and quantum computing—the skill sets and tools you develop are of great value in preparing you to start a company, or to find a job in industry.  I will discuss briefly the two companies I have founded, provide an overview of the technology of each, what it takes to get going, and the lessons learned in doing so.

October 26 — "Exploiting Disorder for Global and Local Response"

• Presenter: Sidney Nagel, University of Chicago
• Host: Noel Clark
• Abstract: We are customarily taught to understand ordinary solids by considering perturbations about a periodic structure.  This approach becomes increasingly untenable as the amount of disorder in the solid increases.  In a crystal with only one atom per unit cell, all atoms play the same role in producing the solid's global response to external perturbations. Disordered materials are not similarly constrained and a new principle emerges: independence of bond-level response. This allows one to drive the system to different regimes of behavior by successively removing individual bonds. We can thus exploit disorder to achieve unique, varied, textured and tunable global response. We can use similar pruning techniques to achieve long-range interactions inspired by allosteric behavior in proteins. This allows a local input strain to control the local strain at a distant site in the network.

November 2 — "A Bridge Too Far: The Demise of the Superconducting Super Collider"

• Presenter: Michael Riordan, Author
• Host: Allan Franklin
• Abstract: In October 1993 the US Congress terminated the Superconducting Super Collider — at over $10 billion the largest and costliest basic-science project ever attempted.  It was a disastrous loss for the nation’s high-energy physics community. With the 2012 discovery of the Higgs boson at CERN’s Large Hadron Collider, Europe has assumed world leadership in this field.
  A combination of fiscal austerity, continuing SSC cost overruns, intense Congressional scrutiny, lack of major foreign contributions, waning Presidential support, and the widespread public perception of mismanagement led to the project’s demise nearly five years after it had begun. Its termination occurred against the political backdrop of changing scientific needs as US science policy shifted to a post-Cold War footing during the early 1990s. And the growing cost of the SSC inevitably exerted undue pressure upon other worthy research, thus weakening its support in Congress and the broader scientific community.
  As underscored by the Higgs boson discovery, at a mass substantially below that of the top quark, the SSC did not need to collide protons at 40 TeV in order to attain its premier physics goal. The selection of this design energy was governed more by politics than by physics, given that Europeans could build the LHC by eventually installing superconducting magnets in the LEP tunnel under construction in the mid-1980s. In hindsight, there were good alternative projects the US high-energy physics community could have pursued that did not involve building a gargantuan, multibillion-dollar machine at a green-field site in Texas.

November 9 — "The physics of cell division"

• Presenter: Meredith Betterton, University of Colorado Boulder
• Host: John Price
• Abstract: Cells are the basic unit of life. All life on earth depends on cells’ ability to duplicate themselves. In order to divide successfully, cells must solve fascinating physics problems, which this talk will introduce assuming no biology background. A key step in cell division is ensuring that each of the daughter cells inherits a single copy of the genetic material. In eukaryotes, a self-organized machine called the mitotic spindle exerts forces that physically move the chromosomes. This cellular machine is composed of microtubules, molecular motors, and associated molecules. We are using theory, simulation, and experiment to address fundamental physics questions related to mitosis, including how the mitotic spindle structure self assembles and achieves the correct size, how the spindle organizes and moves chromosomes, and how these same components outside of cells can create nonequilibrium materials that exhibit new physics.

November 16 — "What’s next after Moore’s law: quantum computing"

• Presenter: John Martinis, Google and UC Santa Barbara
• Host: John Price
• Abstract: As microelectronics technology nears the end of exponential growth over time, known as Moore’s law, there is a renewed interest in new computing paradigms such as quantum computing. After many years of fundamental research on superconducting quantum devices, I recently moved my research program to Google with the goal of building a useful quantum computer. Following Feynman’s vision, I will highlight a proof-of-principle experiment to simulate a chemical reaction that finds an interaction cross section. I will also outline a “quantum supremacy” experiment that will demonstrate the exponential power of a quantum processor by checking its output with a classical computer, which is intractable for even the world's most advanced classical supercomputer beyond 45-50 qubits. We are working to perform this experiment in the next year.
  John Martinis currently heads the quantum-hardware team at Google. John started the field of research on quantum devices as a graduate student at UC Berkeley in 1985, and has continued this research at NIST Boulder, UC Santa Barbara, and now Google. In 2010 he was awarded the AAAS science breakthrough of the year, and in 2014 was awarded the London Prize for low-temperature physics research.

November 23 — Fall Break; No Colloquium

November 30 — "Transport and Localization in many-body nuclear spin systems"

• Presenter: Paola Cappellaro, Massachusetts Institute of Technology
• Host: Ana Maria Rey
• Abstract: A large-scale quantum computer could solve problems that would take classical computers longer than the age of the universe to crack, with profound implications for cryptography, chemistry, material science, and many areas of physics. However, to reach this goal we need to control large quantum systems, where the many-body dynamics becomes often fragile and very complex.
  Among the many questions and challenges that arise when working toward this goal, I will address two questions in my talk: How can we transfer quantum information from one quantum register to another?
  How can we preserve quantum information in the presence of strong interactions?
  Using a nuclear spin chain as an exemplary experimental system, and the tools of Hamiltonian engineering, I will show how spin chains can act as quantum wires in a distributed quantum computing architecture, transporting information and entanglement. I will then show how disorder can quench the transport of information, a phenomenon known as localization. This phenomenon might actually be a feature in some situations, as it allows preserving local quantum information for later retrieval and prevents thermalization. Is localization however possible even in the presence of long-range interaction? I will show experimental signatures that a logarithmic growth of long-range correlation is still present in interacting systems, a sign of many-body localization.

**Special Colloquium: Monday, December 5 at 4:00 p.m.** — "Symmetry, Topology and Bacteria"

• 
  NOTE SPECIAL LOCATION: DUAN G125
• Presenter: Ivan Smalyukh, University of Colorado Boulder
• Abstract: Einstein introduced the “colloidal atom” paradigm, but only high-symmetry colloidal crystals could be realized within a century or so. Born developed a theory of polar ordered fluids, but only nonpolar ones could be observed. Heisenberg proposed 3D solitons as models of particles in continuous fields, but Derrick put forward a theorem that they cannot be stable. I will discuss how, addressing these long-standing challenges, we realize the lowest symmetry triclinic colloidal crystals [1] and biaxial ferromagnetic fluids [2], as well as the static 3D topological solitons within them [3]. With production aided by bacteria, such unusual materials promise a solution to the window inefficiency problem and other technological uses.
  1. H. Mundoor, B. Senyuk & I.I. Smalyukh. Science352, 69 (2016).
  2. Q. Liu, P.J. Ackerman, T.C. Lubensky & I.I. Smalyukh. PNAS 113, 10479 (2016).
  3. P.J. Ackerman & I.I. Smalyukh. Nature Mater. DOI:10.1038/NMAT4826 (2016).

For more information about colloquia this semester, contact: John Price.