Eugene Wigner, a Nobel Prize-winning mathematical physicist, once said, “The miracle of the appropriateness of the language of mathematics for the formulation of the laws of physics is a wonderful gift which we neither understand nor deserve.”

Indeed, mathematics may seem abstract or even irrelevant until it’s used to describe the natural world around us. The reverse is occasionally also true: Physical realities, when brought to a mathematician’s attention, can inspire new questions and new discoveries. 

The research of Alicia Kollár, a Chesapeake Assistant Professor of Physics at the University of Maryland and a Fellow of the Joint Quantum Institute, embodies the give and take of this relationship between physics and mathematics. In her lab, she brings abstract theories to life and in turn collaborates on new theorems. She has forged a research program of manipulating light on a chip, coaxing the light into behaving as though it lives on the surface of a sphere, or a mathematical abstraction known as a hyperbolic surface. She also collaborates with mathematicians, furthering both the understanding of what these chips can do and their underlying mathematics. 

Alicia KollárA direct collaboration with pure mathematicians is uncommon for a physicist, particularly an experimentalist. But Kollár is no stranger to mathematics. Raised by two mathematicians in Princeton, New Jersey, she was exposed to the discipline early on. However, Kollár said her parents didn’t pressure her to pursue mathematics growing up. 

“It never crossed my dad’s mind to try to force me to do what he loved,” Kollár said. “He considered that pointless, like ‘You should go into research for you, not for somebody else’s expectations.’” 

Her father, János Kollár, a professor of mathematics at Princeton, had a slightly different take. 

“She was always interested in science, so I didn’t need to apply any influence,” he said. “If she was only interested in rock music it might have been different.”

Free to pursue whatever she pleased (short of rock music), Kollár studied advanced math, but without much enthusiasm. 

“I was fortunate to be able to take quite a bit of college-level pure math as a high schooler,” she said. “And I would say that I think I was good at it, but I didn’t love it. I just kind of didn’t care.” 

What really caught Kollár’s attention was physics. Her high school physics teacher’s style really resonated with her. 

“He was a crusty old dude that loved Far Side cartoons,” she recalled. “And he wouldn’t put up with anybody that was too cool for school. He taught non-calculus physics, but he taught that you have to think about it—not ‘Here’s a method learn how to do it.’ We became really good friends, and I really liked thinking about how it works, you know, the physical intuition part of physics.”

She attended college at Princeton University, remaining in her hometown and further developing her fascination with physics. 

“I was sort of divided between math and physics as a freshman,” Kollár said. “But the more physics I took, I never looked back.”

During her first summer research experience, she was charged with taking apart a telescope mount for a cosmology group. That’s when she found her calling as an experimentalist.  

“I had a lot of fun that summer,” she said, smiling. “I ended up building a 1500-pound steel support structure. I was up to my eyeballs in machine oil and loving every minute of it.”

When applying to graduate schools, Kollár’s soon-to-be Ph.D. adviser Benjamin Lev, now an associate professor of physics and applied physics at Standford University, called her and convinced her to join his lab. He enticed her with the promise that, as an atomic and optical physicist, she could do both theory and experiment side by side. She joined his group at the University of Illinois at Urbana-Champaign, and, in her first year, moved with the whole team to Stanford.

Kollár’s Ph.D. work consisted of building a novel experimental apparatus from scratch, designed to trap atoms and photons together and allow them to influence each other in significant, controllable ways. The resulting experimental setup launched a new direction in its field, according to Lev. 

“From beginning to end, it was just an amazing graduate school experience, where you see something from the inception of the idea to actually showing that this new experimental technique can work,” Lev said. “And she was always a thought partner. We were thinking through the ideas, writing the equations on the board, working with theorists, and she was an equal thought partner on all of that.”

After graduate school, Kollár found herself returning to Princeton. “Princeton is a black hole,” she said. “You can never quite leave. Maybe it’s the Hotel California, you know?”

She became a postdoctoral researcher in the lab of Andrew Houck, a professor of electrical and computer engineering and a Fellow in the Princeton Center for Theoretical Science. Houck worked with coplanar waveguides—little paths printed on a circuit board that confine light in a tube the thickness of a human hair. These paths have become the setting of many of Kollár’s mathematical explorations. 

Kollár was in her office one day, playing around with one of these coplanar waveguide chips. This one contained a waveguide lattice—a repeating grid, one waveguide after the other. Lattices are a familiar concept to physicists from the study of metals, where atomic nuclei form repeating patterns, extending in all three directions.

Kollar’s mathematical training bubbled up, flooding her brain with ideas. She envisioned a similar lattice, but instead of one dimension it would extend in two. And, she realized, thanks to the properties of coplanar waveguides, there was a lot of flexibility in the ways she could shape these grids.  

Instead of being points, as in a conventional lattice of nuclei in a metal, the sites of this lattice were paths—lines that guide light around. And, Kollár could bend and stretch these lines however she wanted without changing the underlying physics, as long as the total length stayed the same. 

Kollár realized that by scrunching and stretching these waveguides, she could connect them to each other in ways that aren’t possible for normal lattices of points, at least not in the world we are used to. Instead, the waveguides would act as though they are on the surface of a sphere, or a mathematical construction known as a hyperbolic surface, where traditional ideas of parallel lines, triangles and navigation break down.  

A hyperbolic surface is, in a sense, the opposite of a sphere. So much so that a two-dimensional hyperbolic surface can’t exist within our three-dimensional world—basically, it doesn’t fit. Kollár said the best way to imagine hyperbolic space is with some of M. C. Escher’s pictures. 

Kollár and her collaborators successfully showed that coplanar waveguides can indeed form lattices that act as though they live on a hyperbolic surface. 

Kollár found that these hyperbolic lattices had some cool physics properties. In particular, she found that they gave rise to something called flat bands—paradoxical places where, regardless of how fast a particle is moving, its energy stays the same. These flat bands are thought to be behind some of the most intriguing unexplained physical effects, like the fractional quantum Hall effect, spin-​liquids, and even some cases of high-temperature superconductivity. 

“When I discovered these flat bands, I actually thought I made a mistake in my code,” Kollár said, “I turned around to my lab partner, and I was like, ‘I think I messed up but if I didn’t, this is really cool.’ And so at the time, we didn't understand where that was coming from. What we've since come to understand is that was really just the tip of the iceberg.”

To understand the full potential of this new technique, Kollár joined forces with Peter Sarnak, professor of mathematics at the Institute for Advanced Study at Princeton. This collaboration has proved extremely fruitful. Together, they showed that the flat bands were far from a mistake. In fact, they proved that the flat bands must exist in any hyperbolic lattice of the kind Kollár creates.

“There's been this constant feedback between very general math theorems leading to good examples and then good examples leading to new math theorems,” Kollár said.

Now, she is leading her own group at UMD and is working on coupling bits of quantum information—called qubits—to these exotic lattices. She has assembled a group of like-minded students, interested in addressing novel physics. Although there’s no way to know exactly what the future holds for Kollár, it’s fair to anticipate that she will continue to follow her nose to interesting and unexpected places. 

“I think what was special about Alicia is that she always had her own mind and she did not want to follow what others were doing,” her father, János, said. “It can be frustrating when you're a two-year-old, but I think in the long run if you can follow your own mind very seriously it can work out very well.”

Written by Dina Genkina

When University of Maryland senior physics majors Ela Rockafellow and Kate Sturge entered the lecture hall of their honors math course freshman year, they quickly realized they were two of three women in a room of about 25 people.

All through high school, Rockafellow noticed how the number of women, gender minorities and students of color diminished in her advanced STEM classes, especially physics and math. When she asked her friends why their passion for science had faded, they told her they didn’t feel smart enough for the coursework—and often mentioned specific experiences or interactions that had discouraged them.

Studies show that since the ’90s, young women and men have earned about the same number of math and science high school credits, with women performing slightly better than men in these classes. But men are more likely to take the advanced placement exams to receive college credit. Seeing this themselves, Rockafellow and Sturge wondered how the dynamic could be changed so young members of underrepresented groups would feel empowered to pursue their goals in STEM.

“I think everyone in physics has felt like they’re not smart enough at one point or another,” said Rockafellow, a 2021 Goldwater Scholar. “But the compounded effect of society’s assumption that certain people aren’t as intelligent as others, especially in STEM spaces, can make it significantly more difficult to stay in the field.” 

Crafting a Curriculum

Rockafellow and Sturge, now co-presidents of the Society of Physics Students (SPS), decided to develop a class that would provide undergraduate students with the tools to counter society's assumptions about students in STEM. The idea for the course had initially been raised by attendees in an SPS town hall meeting in fall 2020. As SPS co-presidents, Rockafellow and Sturge decided to push the concept forward and create the course themselves in close collaboration with the director of education for the Department of Physics, Donna Hammer.

For months, Rockafellow and Sturge brainstormed the right course structure with Hammer, determining the necessary elements to make the course a reality. Together, they landed on a one-credit speaker series seminar to pilot the class, which became PHYS 298D: Diversity, Equity and Inclusion in Physics. 

“The idea was that from listening to a variety of speakers, students would gain a broader perspective, both validating the experience of minority students and increasing empathy and understanding of what minority members of the physics community go through,” Rockafellow explained. “Once we put together a rough outline for a curriculum, we sent it to everybody we knew who knew had experience in DEI work, and we got tons of feedback on how to make the course most effective.” 

To host this seminar, Rockafellow and Sturge first needed to find speakers. Starting with the American Physical Society’s climate report author list, they emailed hundreds of DEI experts to find the right mix of perspectives.

“We ended up getting a lot of really well-known people in the field to come speak just from asking,” Sturge said.

Speakers they chose ranged from Sandy Springs Friends School Head of School Rodney Glasgow to Harvard University Department of the History of Science Chair Evelynn Hammonds to UMD Counseling Center Research Director Yu-Wei Wang. Rockafellow and Sturge publicized the speaker series to SPS and physics department faculty and staff, expanding the reach of each lecture to the greater UMD physics community.

“The seminar format was a natural fit and an exciting student-driven curriculum endeavor,” Hammer said. “Ela and Kate have excellent leadership skills and true dedication to addressing and solving DEI issues.”

When freshman physics major Alejandro Escoto registered for PHYS 298D, he already had some understanding of the challenges underrepresented minorities have faced in physics. But he didn’t realize just how extensive those challenges were. 

“In this class, we explored in-depth why women and people of color have been excluded in physics, how it continues to happen and what each individual can do on a small scale to change that narrative,” Escoto said. “I left the class with a better understanding of how my own privileges play into my navigating of the field and how the things I say will end up affecting other people.”

Plotting the Future Course

For the course’s final project, students proposed projects to advance DEI efforts in their academic communities. For example, Escoto proposed a follow-up course to PHYS 298D on the history of science, focusing on the achievements of a wide range of scientists rather than just white men. 

“There’s a culture of there being one type of physicist,” Sturge said. “Usually, that physicist is white, male, cisgender, straight. That’s the box that you have to fit in. It’s our responsibility to use our privilege as white women to speak up and work toward a goal of dismantling that ideology in physics.” 

With the successful pilot behind them, Rockafellow and Sturge are looking for ways to grow the size of the course the next time it’s taught and they’re revising the PHYS 298D curriculum to meet the Understanding Plural Societies general education requirements. They also hope to continue their outreach work toward building a more diverse, inclusive physics community as they apply to graduate school.

“When you have a bunch of diverse minds together, science really flourishes,” Sturge said. “That’s why this work is important. We’re all working toward a better physics community.”

 Written by Katie Bemb

Thomas Ferbel, a UMD visiting professor since 2013, died at his home on Saturday, March 12. He was 84.

Ferbel was born in 1937 in Radom, Poland. During the tumult of World War II, he and his family endured exile in a Russian gulag and later, a camp for displaced persons in Stuttgart. Eventually, Ferbel arrived in New York and received a B.A. in Chemistry from Queens College, CUNY, and his and Ph.D. in Physics from Yale University (where his favorite professor was Bob Gluckstern, later the chancellor of this campus and a professor of physics).Thomas Ferbel

After a postdoctoral appointment at Yale, Ferbel accepted a faculty position at the University of Rochester in 1965.  While there, he received an Alfred P. Sloan Fellowship, a John S. Guggenheim Fellowship and an Alexander von Humboldt Prize.

He was elected a Fellow of the American Physical Society in 1984, and served as the U.S. program manager for the Large Hadron Collider from 2004-08.

In 2020, Ferbel described both his early years and his life as a physicist as part of the American Institute of Physics Oral History project. The transcript is available here: https://www.aip.org/history-programs/niels-bohr-library/oral-histories/46304

There is nothing permanent except change. This is perhaps never truer than in the fickle and fluctuating world of quantum mechanics.

The quantum world is in constant flux. The properties of quantum particles flit between discrete, quantized states without any possibility of ever being found in an intermediate state. How quantum states change defies normal intuition and remains the topic of active debate—for both scientists and philosophers.

For instance, scientists can design a quantum experiment where they find a particle’s spin—a quantum property that behaves like a magnet—pointing either up or down. No matter how often they perform the experiment they never find the spin pointing in a direction in between. Quantum mechanics is good at describing the probability of finding one or the other state and describing the state as a mix of the two when not being observed, but what actually happens between observations is ambiguous.In the figure, a path winds through an abstract landscape of possible quantum states (gray sheet). At each point along the journey, a quantum measurement could yield many different outcomes (colorful distributions below the sheet). A new theory places strict limits on how quickly (and how slowly) the result of a quantum measurement can change over time depending on the various circumstances of the experiment. For instance, how precisely researchers initially know the value of a measurement affects how quickly the value can change—a less precise value (the wider distribution on the left) can change more quickly (represented by the longer arrow pointing away from its peak) than a more certain value (the narrower peak on the right). Credit: Schuyler Nicholson

This ambiguity extends to looking at interacting quantum particles as a group and even to explaining how our everyday world can result from these microscopic quantum foundations. The rules governing things like billiards balls and the temperature of a gas look very different from the quantum rules governing things like electron collisions and the energy absorbed or released by a single atom. And there is no known sharp, defining line between these two radically different domains of physical laws. Quantum changes are foundational to our universe and understanding them is becoming increasingly important for practical applications of quantum technologies.

In a paper(link is external) published Feb. 28, 2022 in the journal Physical Review X, Adjunct Assistant Professor Alexey Gorshkov, Assistant Research Scientist Luis Pedro García-Pintos and their colleagues provide a new perspective for investigating quantum changes. They developed a mathematical description that sorts quantum behaviors in a system into two distinct parts. One piece of their description looks like the behavior of a quantum system that isn’t interacting with anything, and the second piece looks like the familiar behavior of a classical system. Using this perspective, the researchers identified limits on how quickly quantum systems can evolve based on their general features, and they better describe how those changes relate to changes in non-quantum situations.

“Large quantum systems cannot in general be simulated on classical computers,” says Gorshkov, who is a Fellow of the Joint Quantum Institute (JQI)  and the Joint Center for Quantum Information and Computer Science (QuICS). “Therefore, understanding something important about how these systems behave—such as our insights into the speed of quantum changes—is always exciting and bound to have applications in quantum technologies.”

There is a long history of researchers investigating quantum changes, with most of the research focused on transitions between quantum states. These states contain all the information about a given quantum system. But two distinct states can be as different as can be mathematically despite being extremely similar in practice. This means the state approach often offers a perspective that's too granular to generate useful experimental insights.

In this new research, the team instead focused on an approach that is more widely applicable in experiments. They didn’t focus on changes of quantum states themselves but rather on observables—the results of quantum measurements, which are what scientists and quantum computer users can actually observe. Observables can be any number of things, such as the momentum of a particle, the total magnetization of a collection of particles or the charge of a quantum battery(link is external) (a promising but still theoretical quantum technology). The researchers also chose to investigate quantum behaviors that are influenced by the outside world—a practical inevitability.

The team looked at general features of a possible quantum system, like how well known its energy is and how precisely the value they want to look at is known beforehand. They used these features to derive mathematical rules about how fast an observable can change for the given conditions.

“The spirit of the whole approach is not to go into the details of what the system may be,” says García-Pintos, who is also a QuICS postdoctoral researcher and is the lead author on the paper. “The approach is completely general. So once you have it, you can ask about a quantum battery, or anything you want, like how fast you're able to flip a qubit.”

This approach is possible because in quantum mechanics, two quantities can be intricately connected with strict mathematical rules about what you can know about them simultaneously (the most famous of these rules is the Heisenberg uncertainty principle for a quantum particle’s location and speed).

In addition to their new limits, they were able to reverse the process to show how to make a system that achieves a desired change quickly.

These new results build upon a previous work(link is external) from García-Pintos and colleagues. They studied classical changes such as how quickly energy and entropy can be exchanged between non-quantum systems. This previous result allowed the researchers to break up different behaviors into quantum-like and non-quantum-like descriptions. With this approach, they have a single theory that spans the extremes of possible outside influence—from enough interaction to allow no quantum behavior to the purely theoretical realms of quantum situations without any external influence.

“It's nice; it's elegant that we have this framework where you can include both of these extremes,” García-Pintos says. “One interesting thing is that when you combine these two bounds, we get something that is tighter, meaning better than the established bound.”

Having the two terms also allowed the researchers to describe the slowest speed at which a particular observable will change based on the details of the relevant situation. In essence, to find the slowest possible change they look at what happens when the two types of effects are completely working against each other. This is the first time that a lower bound has been put on observables in this way.

In the future, these results might provide insights into how to best design quantum computer programs or serve as a starting point for creating even more stringent limits on how quickly specific quantum situations can change.

Original story by Bailey Bedford: https://jqi.umd.edu/news/new-perspective-blends-quantum-and-classical-understand-quantum-rates-change

In addition to Gorshkov and García-Pintos, authors on the paper include Schuyler Nicholson, a postdoctoral fellow at Northwestern University; Jason R. Green, a professor of chemistry at the University of Massachusetts Boston; and Adolfo del Campo, a professor of physics at the University of Luxembourg.

Elizabeth Bennewitz, a first-year physics graduate student at JQI and QuICS, has been named a finalist for a 2022 Hertz Fellowship. Out of more than 650 applicants, Bennewitz is one of 45 finalists with a chance of receiving up to $250,000 in support from the Fannie and John Hertz Foundation.

The fellowships provide up to five years of funding for recipients pursuing a Ph.D. The foundation seeks(link is external) individuals who intend to tackle “major, near-term problems facing society.”Elizabeth Bennewitz (credit: Dan Spencer)

“This whole group of finalists have accomplished so much, and I’m very humbled to be among other people starting their Ph.D.s who are also pursuing big problems in science,” says Bennewitz. “I'm very honored to be part of this finalist group.”

Bennewitz is working with JQI and QuICS Fellow Alexey Gorshkov and is interested in researching large collections of interacting quantum particles—what scientists call many-body quantum systems. These systems are important to understanding cutting-edge physics and quantum computer technologies and can also be the basis of simulations that could provide insights into complex problems in physics, material science and chemistry.

“During my PhD, I want to develop tools and techniques that help harness the computational power of quantum devices in order to simulate these large quantum many-body systems,” Bennewitz says. “I’m excited to be pursuing this research at Maryland because of its commitment to quantum information and quantum computing research as well as its rich collaboration between theorists and experimentalists.”

Bennewitz is just at the beginning of her graduate student career, but she has already started investigating how quantum simulators might be used to understand the interactions of the particles that are responsible for holding the nuclei of atoms together.

“I'm very happy for Elizabeth, and I'm honored and excited that she chose to work with my group,” Gorshkov says.

An announcement of the winning fellows is expected to be made in May.

“I'm very thankful for all the opportunities I had before I got here,” Bennewitz says. “I would not be where I am today without the support and guidance I received from my professors and peers at Bowdoin College and Perimeter.”

Original story by Bailey Bedford: https://jqi.umd.edu/news/jqi-graduate-student-finalist-hertz-fellowship