Lathrop Lab's Geodynamo Set for Overhaul

In a hangar-sized laboratory off Paint Branch Drive, Dan Lathrop gives the signal, and what he often calls simply “the experiment” awakens. A huge, steel sphere with tubes and electrical wires snaking across its surface begins a stately, nearly silent rotation inside a towering cage-like structure.

That’s the experiment running at visitor speed, however. When only Lathrop, a Distinguished Scholar-Teacher and professor in physics, and his graduate students are present to gather data, they crank up its 350 horsepower electric motor to spin 80 times faster, until the 3-meter globe encasing 25,000 pounds of liquid sodium blurs out at four revolutions per second.geodynamo 1920x1080Professor Dan Lathrop examines the 3-meter steel sphere he uses in simulations of the Earth's "geodynamo." Hidden inside the spinning outer sphere (diagram, below) molten sodium and an even quicker-whirling inner sphere represent the earth's liquid outer core and solid inner core, which create geomagnetism. (Photo by John T. Consoli; diagram by Kolin Behrens)

For safety reasons, in the 11 years since he first switched the experiment on, no lab guest has ever watched it run that fast. Lathrop hasn’t either, exactly. “You can’t see it at full speed,” he said.

If “the experiment” sounds pretty singular, that’s because there’s nothing else like it on the planet. Lathrop, an expert in turbulent flows, envisioned the giant apparatus and several smaller predecessors as a way to simulate and perhaps even predict changes in the Earth’s magnetic field, which originates in its core and helps protect the surface from harmful solar radiation. While the machine has fascinated the geophysics community and generated useful results about planetary magnetic fields, it has never quite fulfilled Lathrop’s hopes. So this year, supported by a recently renewed National Science Foundation grant, he and his lab members will undertake a painstaking process to drain the flammable sodium, dismantle the device, upgrade it and—if the plan works—create a better magnetic model of the Earth.

Our planet has a “ggeodynamo diagrameodynamo,” a self-generating, self-sustaining magnetic field created by flows in its molten outer core, a layer of mostly iron and nickel more than 3,000 kilometers beneath our feet. Swirling turbulence in the liquid metal, caused by convection and the planet’s rotation, gives rise to electrical currents and magnetic fields that feed on each other.

So far, Lathrop’s experiment needs external current to generate a magnetic field; soon he hopes that will no longer be necessary. Doctoral students Rubén Rojas and Artur Perevalov in physics, along with Heidi Myers in geology and Sarah Burnett in mathematics, have been researching ways to modify a hidden, inner sphere of the device—analogous to Earth’s solid inner core—by adding texture to create swirling, helical flows in the highly conductive liquid sodium, generating electrical currents.

It’s never been tried before, so the results are hard to predict.

“I try not to be a foolish optimist, but you know, you aren’t going to build an experiment like this without a certain amount of optimism that there are interesting things to see,” Lathrop said.

The biggest potential prize would be an ability to predict the “weather” of Earth’s magnetic field, which is constantly in flux. Geologic evidence suggests the poles have reversed hundreds of times—most recently 780,000 years ago—and indeed, the North Pole has been moving from Canada toward Russia with increasing speed in recent years. During such a flip, much of the planet’s surface could have a weaker magnetic shield from solar radiation. (For a preview of what that could be like, look at Mars, which lacks a geodynamo.)

Even now, solar storms do create problems on Earth, damaging satellites and sensitive electronics, said Sara Gibson, a solar physicist at the National Center for Atmospheric Research in Boulder, Colo. For instance, if a massive 1859 solar storm that caused aurora as far south as the tropics hit today, it could fry communications and electrical grids worldwide.

“Dan’s work is really important, because it’s vital to understand the Earth’s magnetic field, which is coupling with what’s coming from the sun, and creating these magnetic impacts,” Gibson said.

Lathrop doesn’t promote his research with disaster scenarios. A pole reversal may not be in the offing at all, and would take more than 1,000 years. But what about scientific curiosity as well as simple prudence concerning a factor that allowed life to arise on earth?

“You think you’d want a solid scientific base knowing, well, how does it work, and how did it get there?” he said. “Where’s it at now? And where’s it going?”

Original story by Chris Carroll, Maryland Today 

Watch the 3 meter experiment.

Physics Professors Selected for MURI Awards

The Department of Defense (DoD) announced 26 2020 Multidisciplinary University Research Initiative (MURI) awards totaling $185 million, and the University of Maryland tied with the University of Illinois for the highest university representation on the list. 
 

The MURI program complements other DoD basic research efforts that support traditional, single-investigator university research grants. By supporting multidisciplinary teams with larger and longer awards in carefully chosen topics identified for their long-term importance, DoD and the military services boost the potential for significant and sustained advancement of the research in critical areas.

Associate Professor Mohammad Hafezi and JQI postdoctoral researcher Sunil Mittal are participating in a project named “Robust Photonic Materials with High-Order Topological Protection” headed by Gaurav Bahl at the University of Illinois. This work, sponsored by the Office of Naval Research (ONR), will explore techniques for manipulating light in interesting ways—such as restricting it to the corners of a silicon chip. These techniques often offer some protection to the light’s fragile quantum characteristics. 

Distinguished University Professor Tom Antonsen and Professor Phil Sprangle are members of a team that will investigate “Fundamental Limits of Controllable Waveform Diversity at High Power.” This effort, sponsored by the Air Force Office of Scientific Research (AFOSR), is led by Edl Schamiloglu at the University of New Mexico.

Adjunct Associate Professor Alexey Gorshkov will participate in “New Approaches to Quantum  Control with Individual Molecule Sensitivity” headed by Kang-Kuen Ni at Harvard University. The researchers hope to achieve a high degree of control over individual molecules, similar to the control that scientists already wield over individual atoms. Molecules are built from many atoms, whose chemical interactions ratchet up the challenges of achieving fine control. So the effective manipulation of molecules requires combining the tools and techniques of chemistry with those from physics and quantum information. The work will expand upon Gorshkov’s previous research studying systems that manipulate ultra-cold molecules.
 
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Derived from stories published by UMD ECE and the JQI: 
https://ece.umd.edu/news/story/ece-researchers-represented-on-three-2020-muri-awards
 

Maryland Quantum Alliance Launched

The Maryland Quantum Alliance—a regional consortium of quantum scientists and engineers from across academia, national laboratories and industry—launched on January 29, 2020 with an event in the House of Delegates Office Building, and was recognized on the floor of the Maryland House of Delegates. Members of this alliance will drive quantum science discovery and innovation, develop pioneering quantum technologies and train the quantum workforce of tomorrow for the state of Maryland, the region and the nation. 

The announcement comes at a pivotal time when quantum science research is expanding beyond physics into materials science, engineering, computer science and chemistry. Scientists across these disciplines are finding ways to exploit quantum physics to build powerful computers, develop secure communication networks and improve sensing capabilities. In the future, quantum technology may also impact fields like artificial intelligence and medicine. 

The state of Maryland already leads the way in this crucial transition, with an existing workforce that spans academia, government and private-sector companies. Scientists and engineers at the University of Maryland, College Park and other institutions in the state and region already are collaborating across these areas to tackle the challenges associated with deploying quantum technology. 

“With our great strength in quantum science, computing and innovation, we are well positioned to lead this initiative,” said University of Maryland President Wallace D. Loh. “By combining the strength of neighboring universities, federal labs and businesses, this initiative can make the whole region into a quantum powerhouse.”

Already a major hub for quantum science and technology, UMD hosts five collaborative research centers focused on different aspects of quantum science and technology: The Joint Quantum Institute (JQI) and the Joint Center for Quantum Information and Computer Science (QuICS) are collaborations with the National Institute of Standards and Technology. The Quantum Technology Center (QTC) brings together UMD engineers and physicists to work on translating quantum physics into transformational new technologies. The Condensed Matter Theory Center has made pioneering contributions to topological approaches to quantum computing, and the Quantum Materials Center explores superconductors and novel quantum materials to enable new technology devices.  

UMD played a key role in advocating for last year’s National Quantum Initiative Act that positions quantum information science and technology at the top of the U.S. science and technology agenda and provides $1.275 billion over five years for research. The university also is part of the Quantum Information Edge, a new nationwide alliance of U.S. national labs, universities and industry launched to advance the frontiers of quantum computing systems.

Maryland Quantum Alliance is currently comprised of the University of Maryland, College Park; University of Maryland, Baltimore County; Morgan State University; Johns Hopkins University; George Mason University; The MITRE Corporation; Johns Hopkins University Applied Physics Laboratory; CCDC Army Research Laboratory; Northrop Grumman; Lockheed Martin; IonQ; Qrypt; Booz Allen Hamilton; and Amazon Web Services.

In the alliance, government and academic researchers will look for new ways to work with companies both large and small to support steady progress on quantum technology research and enable its move into the marketplace. 

"Quantum information science will provide important capabilities for our Warfighter,” said Dr. Pat Baker, CCDC Army Research Laboratory Director. “We are excited about a Maryland Quantum Alliance of strong regional institutions in this field to help accelerate research and transformational impact as part of persistent Army modernization."

Maryland Quantum Alliance members will also work on developing cross-disciplinary educational programs in physics, engineering, materials science and computer science that will produce the necessary workforce educated in quantum science. 

Original story by Lee Tune This email address is being protected from spambots. You need JavaScript enabled to view it. 301-405-4679

Catching New Patterns of Swirling Light Mid-flight

In many situations, it’s fair to say that light travels in a straight line without much happening along the way. But light can also hide complex patterns and behaviors that only a careful observer can uncover.

This is possible because light behaves like a wave, with properties that play a role in several interesting phenomena. One such property is phase, which measures where you are on an undulating wave—whether you sit at a peak, a trough or somewhere in between. When two (otherwise identical) light waves meet and are out of phase, they can interfere with one another, combining to create intricate patterns. Phase is integral to how light waves interact with each other and how energy flows in a beam or pulse of light.

Researchers at the University of Maryland, led by UMD Physics Professor Howard Milchberg, have discovered novel ways that the phase of light can form optical whorls—patterns known as spatiotemporal optical vortices (STOVs). In a paper published in the journal Optica on Dec. 18, 2019, the researchers captured the first view into these phase vortices situated in space and time, developing a new method to observe ultra-fast pulses of light.

Each STOV is a pulse of light with a particular pattern of intensity—a measure of where the energy is concentrated—and phase. In the STOVs prepared by Milchberg and his collaborators, the intensity forms a loop in space and time that the researchers describe as an edge-first flying donut: If you could see the pulse flying toward you, you would see only the edge of the donut and not the hole. (See leftmost image below, where negative times are earlier.) In the same region of space and time, the phase of the light pulse forms a swirling pattern, creating a vortex centered on the donut hole (rightmost image).Milchberg 2020 storyProcessed data showing the intensity forming a ring (left) and the phase forming the vortex (right) in a spatiotemporal optical vortex. The green arrow indicates the increase of the phase around the vortex. (Credit: Scott Hancock/University of Maryland)

Milchberg and colleagues discovered STOVs in 2016 when they found structures akin to “optical smoke rings” forming around intense laser beams. These rings have a phase that varies around their edge, like the air currents swirling around a smoke ring. The vortices made in the new study are a similar but simpler structure: If you think of the original smoke ring as a bracelet made of beads, the new STOVs are like the individual beads.

The prior work showed that STOVs provide an elegant framework for understanding a well-known high-intensity laser effect—self-guiding. At high intensity, this effect occurs when a laser pulse, interacting with the medium it’s traveling through, compresses itself into a tight beam. The researchers showed that in this process, STOVs are responsible for directing the flow of energy and reshaping the laser, pushing energy together at its front and apart at its back.

That initial discovery looked at how these rings formed around a beam of light in two dimensions. But the researchers couldn’t explore the internal working of the vortices because each pulse is too short and fast for previously established techniques to capture. Each pulse passes by in just femtoseconds—about a 100 trillion times quicker than the blink of an eye.

“These are not microsecond or even nanosecond pulses that you just use electronics to capture,” says Sina Zahedpour, a co-author of the paper and UMD physics postdoctoral associate. “These are extremely short pulses that you need to use optical tricks to image.”

To capture both the intensity and phase of the new STOVs, researchers needed to prepare three additional pulses. The first pulse met with the STOV inside a thin glass window, producing an interference pattern encoded with the STOV intensity and phase. That pattern was read out using two longer pulses, producing data like that shown in the image above.

“The tools we had previously only looked at the amplitude of the light,” says Scott Hancock, a UMD physics graduate student and first author of the paper. “Now, we can get the full picture with phase, and this is proof that the principle works for studying ultrafast phenomena.”

STOVs may have a resilience that is useful for practical applications because their twisting, screw-like phase makes them robust against small obstacles. For example, as a STOV travels through the air, parts of the pulse might be blocked by water droplets and other small particles. But as they continue on, the STOVs tend to fill in the small sections that got knocked out, repairing minor damage in a way that could help preserve any information recorded in the pulse. Also, because a STOV pulse is so short and fast, it is indifferent to normal fluctuations in the air that are comparatively slow.

“Controlled generation of spatiotemporal optical vortices may lead to applications such as the resilient propagation of information or beam power through turbulence or fog,” says Milchberg. “These are important for applications such as free-space optical communications using lasers or for supplying power from ground stations to aerial vehicles.”

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In addition to Milchberg, Zahedpour and Hancock, graduate student Andrew Goffin was a co-author.

This research was supported by the National Science Foundation (NSF) (Award No. 1619582), the Air Force Office of Scientific Research (Award Nos. FA9550-16-10121 and FA9550-16-10284) and the Office of Naval Research (Award Nos. N00014-17-1-2705 and N00014-17-12778). The content of this article does not necessarily reflect the views of the NSF, the Air Force Office of Scientific Research or the Office of Naval Research.

The paper “Free-space propagation of spatiotemporal optical vortices,” S. W. Hancock, S. Zahedpour, A. Goffin, and H. M. Milchberg was published in Optica on December 18, 2019.

Media Relations Contact: Bailey Bedford, 301-405-9401, This email address is being protected from spambots. You need JavaScript enabled to view it.