This award supports theoretical research on quantum materials where the strong electron-electron interaction leads to unique transport, thermodynamic and magnetic properties. The research agenda addresses both fundamental physics of electronic interactions in complex materials and practical physics of mesoscopic devices relevant for applications in the domain of quantum science with micro and nanostructures.
The conversion of heat into electricity in solid state systems is governed by thermoelectric effects. The thermoelectric transport in quantum materials and devices is at the heart of various modern electronics applications. Over the last decade, transport measurements in atomically thin two-dimensional materials, such as graphene composed of a single layer of carbon atoms, provided overwhelming evidence that the flow of electrons in such systems exhibits hydrodynamic behavior that resembles the flow of a viscous fluid. These advances pushed the limits of hydrodynamics, providing new perspectives on old fundamental problems and opening doors for completely new discoveries of emergent physics phenomena. This project is, in part, devoted to new research on thermoelectric resistance of such systems as they are subjected to magnetic fields. The PI will also extend these studies to other forms of low-temperature electronic behavior in solids such as superconductivity, where electrons flow without any resistance, and magnetism, as well as their coexistence.
This award also supports the PI’s educational and outreach activities. The project places significant emphasis on training graduate and undergraduate students by engaging them in research in a highly collaborative environment with a postdoctoral scholar and colleagues from other groups. The PI will reach out to the public and high-school student audiences through (i) collaboration with the USA Physics Olympiad team to foster new generation of physicists and train high-school students for international scholastic competition and (ii) public education via entertaining Wonders of Physics shows. The PI will also be involved in the scientific coordination of a physics summer school as well as organization of international conferences and workshops.
UW–Madison, industry partners run quantum algorithm on neutral atom quantum computer for the first time
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A university-industry collaboration has successfully run a quantum algorithm on a type of quantum computer known as a cold atom quantum computer for the first time. The achievement by the team of scientists from the University of Wisconsin–Madison, ColdQuanta and Riverlane brings quantum computing one step closer to being used in real-world applications. The work out of Mark Saffman’s group was published in Nature on April 20.
Four University of Wisconsin–Madison students have been named winners of 2022 Barry Goldwater Scholarships, one of the most prestigious awards in the U.S. for undergraduates studying the sciences.
The UW–Madison winners are sophomore Lucy Steffes and juniors Sarah Fahlberg, Elias Kemna and Samuel Neuman.
Each university in the country may nominate up to four undergraduates for the annual award. To have all four candidates win is remarkable, says Julie Stubbs, director of UW’s Office of Undergraduate Academic Awards.
Lucy Steffes is a sophomore from Milwaukee, double-majoring in astronomy-physics and physics with a certificate in German. Her freshman year, Steffes began working with astronomy professor Snezana Stanimirovic on the ALMA-SPONGE project, for which she co-authored two papers recently published in the Astrophysical Journal. The project looks at molecular formation in the interstellar medium to describe potentially star-forming regions. At the end of her freshman year, Steffes earned a Hilldale Undergraduate Research Fellowship to calculate the upper limits of molecular detections in the Magellanic Stream. She spent last summer working at the Green Bank Observatory in West Virginia examining the chemical composition and evolution of two globules in the Helix Nebula. This summer, she will be returning to the observatory to examine neutral atomic carbon across the Helix Nebula. She plans to pursue a Ph.D. in astrophysics.
UW–Madison celebrates the first World Quantum Day, April 14
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Even quantum physicists do not understand quantum physics, or so the saying* goes.
“The worst grade I ever got in any class was my first quarter of quantum mechanics, because it just was weird and I didn’t understand it and I couldn’t get my head around it,” says Shimon Kolkowitz, a UW–Madison physics professor with the Wisconsin Quantum Institute (WQI), who now conducts research in quantum sensing. “It is something you develop some kind of feeling and intuition for over time, so it’s my personal feeling, and the feeling of many, that it’s important to start exposing people to these concepts much earlier [than in college].”
Quantum science is weird because it explains the workings of our world at the sub-atomic level. The classical physical world we experience and understand — the predictable trajectory of a baseball in the air or the Earth rotating around the sun — breaks down at these tiny scales.
Understand it or not, quantum science is here to stay.
“Quantum science is a rapidly-growing area of research and industry, and it’s going to have a number of major impacts on any number of different areas of commerce,” Kolkowitz says. “There’s a huge need to train a growing quantum workforce that can participate in, engage with, and develop these new technologies.”
QuanTime kits include a set of light sources and glow-in-the-dark stars. When participants shine different lights at the stars and observe the differences, they are learning about how light manipulates electrons.
The first-ever World Quantum Day, to be celebrated annually on April 14, is an international, community driven event to spark interest and generate enthusiasm for quantum mechanics. A goal of World Quantum Day is to promote public awareness of the positive impact quantum science has had and will have on society. [The date is taken from Planck’s constant, 4.14 * 10-15 eV · s, a value that is used in many quantum mechanics equations.]
“It’s a day to engage people in quantum science and let them know what is going on in current research, but it’s also a chance to demystify and make quantum science more accessible and available,” says Mallory Conlon, a quantum science outreach coordinator at UW–Madison.
Conlon is working with QuanTime, an educational initiative developed by leading quantum institutions to introduce quantum activities to middle and high school students. Anyone can play QuanTime’s online games, where they will learn about principals such as entanglement and superposition. There is even a quantum chess game.
Physics grad student and artist Aedan Gardill created this coloring page for WQD.
“We also have Wonders of Quantum Physics electron transition kits, and we’re sending out nearly 1000 kits to classrooms across the country,” Conlon says. “It’s an inquiry-based activity where participants learn how we can use light to manipulate atoms and electrons, which is really the underpinnings of how quantum computers work.”
The physics department and WQI will also be celebrating WQD by highlighting several quantum science researchers and sharing the top five quantum stories from the past year on social media. Follow along on Twitter and Instagram (both @UWMadPhysics) to learn more about the exciting quantum research being done at UW–Madison.
UW–Madison and WQI are members of the Chicago Quantum Exchange, the NSF-funded Quantum Leap Challenge Institute HQAN, and the Department of Energy’s National Quantum Information Science (QIS) Research Center Q-NEXT, three collaborative efforts that are advancing quantum information science and engineering, especially in Great Lakes region. Learn more about the research happening across our collaborations by searching #MidwestQuantum on social media.
* Borrowed from quantum physicist Richard Feynman’s quote: “I think I can safely say that nobody understands quantum mechanics.”
Physics & math senior Gage Siebert awarded NSF GRFP
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Gage Siebert
Congratulations to Gage Siebert for being awarded a National Science Foundation Graduate Research Fellowship! Gage is a senior math and physics major who has been conducting research in radio astronomy and cosmology. He is working on the optics of NASA’s EXCLAIM mission and constructing a periodicity search using the Tianlai Radio Array. Gage is also a 2021 Hilldale Fellow and Goldwater Scholar, and has won the department’s Hagengruber Scholarship, Liebenberg Family Scholarship, and Henry & Eleanor Firminhac Scholarship. He plans to attend graduate school but has not decided where yet.
Peter Timbie, Gage’s research advisor, says:
Congratulations Gage on winning one of these exceedingly rare awards! We’re really proud of you,Best of luck with you proposal to search for periodic signals in cosmological survey data and your plans for graduate school.
21 UW–Madison students in total received the fellowship, a highly sought and competitive award. The Graduate Research Fellowship Program supports high-potential scientists and engineers in the early stages of their careers. Each year, more than 12,000 applicants compete for 2,000 fellowship awards.
Awardees from UW–Madison, including both undergraduate and graduate students, represent a variety of specializations across science, engineering, and technology. Another 23 UW–Madison students were recognized with honorable mentions.
The program provides awardees with three years of financial support consisting of a $34,000 annual stipend and a $12,000 education allowance. UW–Madison contributes toward fringe benefits.
Fringe benefits: new technique makes x-rays more laser-like
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Detecting a chemical change is often easy: colors may change, heat may be released, or something may smell different. Seeing reactions at the molecular level is not quite so easy, but knowing exactly when and how chemical bonds form or atoms move around is crucial to understanding chemical processes.
X-ray pulses allow researchers to create real-time movies of chemical reactions at the molecular scale (click on image to see animation)
In a new study published March 15 in Proceedings of the National Academy of Sciences, University of Wisconsin–Madison physics professor Uwe Bergmann and his collaborators have turned ultrafast x-ray pulses into something more akin to an optical laser, with cleaner, directional pulses. Their work may lead to visualizing chemical reactions faster than ever at the atomic scale.
“This work is the first step to do with x-rays the same kind of [techniques] which you do with regular lasers,” says Bergmann, the study’s senior author. “We have opened a time window for looking at chemical processes with attosecond [one billionth of one billionth of a second] precision. It’s a new frontier.”
Uwe Bergmann
Around a decade ago, researchers began using powerful x-ray free-electron lasers, which allow them to make ultrafast movies of molecular changes in real time on the femtosecond scale (one thousand times slower than an attosecond). Compared to visible lasers, which provide clean, single-wavelength beams of light, x-ray lasers are somewhat dirty: they contain multiple wavelengths of light of randomly varying intensity.
“What all scientists have done, and are still doing, is that you just adapt to what you get and then you design your experiments around them,” Bergmann says. “That also means that certain experiments, which in the optical laser regime are now standard, have not been possible.”
Bergmann and his colleagues somewhat accidentally discovered a way to make x-rays more like an optical laser. In their experimental setup, they shine intense but dirty x-ray pulses at a manganese sample. When these pulses hit a manganese atom, a lower-level electron is ejected and the hole it leaves is rapidly filled by a higher-level electron. The energy difference is emitted as a photon of a characteristic color. Very intense pulses can create enough of these holes. An emitted photon can effectively stimulate the emission of another one, leading to an avalanche of stimulated X-ray emission, mostly in the forward direction towards their detector.
Every so often, the detector that captures these stimulated emissions showed something they were not expecting: strong fringes, the characteristic pattern that results from constructively and destructively interfering signals. The fringes suggested that they had observed two x-ray emission pulses, separated by only a few femtoseconds.
“We were confused,” Bergmann says. “How did such a pair of x-ray pulses come about?”
After many discussions, calculations, and simulations, the team ruled out many possible explanations, until they finally realized what had happened: occasionally, two of the many spikes in the dirty pulses were much stronger than the rest of them. When these strong spikes occurred a few femtoseconds apart, and each had enough intensity, a clean pair of stimulated x-ray emission pulses emerged.
Two strong x-ray pulses hit the manganese sample, are stretched through the monochromator, and overlap, leading to the characteristic fringes.
Before these two pulses reach the detector, they first travel through a monochromator — essentially a prism that stretches light, much like how white light passing through a clear prism is stretched into a rainbow. These stretched pulses then overlap timewise, and those frequencies that are in phase with each other can add up to become more intense or cancel each other out into dark troughs. Hence, the fringes.
“At times, each signal is rather clean and of similar strength, and one obtains very strong interference fringes,” Bergmann says. “We know that the fringe spacings are directly related to the time difference of the two pulses, and because we can measure them very precisely, we can obtain their time difference with extreme, attosecond precision.”
Currently, these pulse pairs are generated very rarely, Bergmann and his collaborators will work with the accelerator scientists to find ways to manipulate the ‘dirty’ pulses and enhance the chance of producing the pairs. They are optimistic that their work opens the door to new applications of such x-ray pulse pairs — the types of techniques that are used commonly with visible laser light.
“We’re trying to move nonlinear laser optics into the x-ray regime,” Bergmann says. “In the x-ray regime, you can probe certain phenomena that you just cannot optically access. X-ray wavelengths are comparable to the distances between atoms, and we can knock out lower-level electrons to get element specificity with them.”
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Bergmann’s contribution to this research was funded in part by the U.S. Department of Energy, Laboratory Directed Research and Development program at SLAC National Accelerator Laboratory (DE-AC02-76SF00515). Other authors were supported by various funding as described in the study.
Massive bubbles at center of Milky Way caused by supermassive black hole
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The enormous clouds of material known as the eRosita and Fermi bubbles extend above and below the galactic plane of the Milky Way. NASA/KAREN YANG/MATEUSZ RUSZKOWSKI/ELLEN ZWEIBEL
New research reveals the origins of enormous bubbles of material emanating from the center of the Milky Way.
The related structures — known as the eRosita and Fermi bubbles and the microwave haze — are the result of a powerful jet of activity from the supermassive black hole at the center of the galaxy. The study, published March 7 in Nature Astronomy, also shows the jet began spewing out material about 2.6 million years ago, and lasted about 100,000 years.
Ellen Zweibel
The work was led by Karen Yang of National Tsing Hua University in Taiwan with University of Wisconsin–Madison astronomer Ellen Zweibel and Mateusz Ruszkowski at the University of Michigan.
The black hole origin of these huge bubbles rules out an alternative model that the expansion of the material was driven by exploding stars. Such a nuclear starburst would last about 10 million years, according to Zweibel, a professor of astronomy and physics at UW–Madison.
“On the other hand, our active black hole model accurately predicts the relative sizes of the eRosita X-ray bubbles and the Fermi gamma ray bubbles, provided the energy injection time is about one percent of that, or one-tenth of a million years,” Zweibel says. “Injecting energy over 10 million years would produce bubbles with a completely different appearance. While both the black hole and stellar explosion models were in reasonably good agreement with the gamma ray data, it’s the discovery of the X-ray bubbles, and the opportunity to compare the X-ray and gamma ray bubbles, which provide the crucial, previously missing piece.”
The enormous structures are nearly 36,000 light-years tall, one-third the diameter of the Milky Way. The eRostia and Fermi bubbles were named for the telescopes that discovered them in 2020 and 2010, respectively.
Sridhara Dasu named a member of the International Committee on Future Accelerators
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High energy physicist Sridhara Dasu was recently named a member of the International Committee for Future Accelerators (ICFA), a term he’ll serve for three years. ICFA was created to facilitate international collaboration in the construction and use of accelerators for high energy physics. The Committee has 16 members, selected primarily from the regions most deeply involved in high-energy physics. Dasu will be representing the United States on the committee.
Blending the rules: how physics helps paint a new picture for artists of all mediums
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This post was written by Rachael Lee, a student science writer with University Communications.
A singer or a violinist’s performance produces sound waves that echo across a concert hall. A painter may mix different paint colors to create a new hue. Dancers use forces like gravity and inertia to produce stunning displays.
At first glance, the arts and physical sciences may look like very separate disciplines. However, many art forms are based on physics.
One hugely popular physics course at the University of Wisconsin–Madison shows how the arts and physics are, in fact, inextricably linked. Physics in the Arts (Physics 109) examines sound and light using examples from the arts. Physics in the Arts has been taught at UW–Madison since 1969, when it was started by physics professors Willy Haeberli and Ugo Camerini. Today’s instructors, professors Pupa Gilbert and A. Baha Balantekin, are continuing and extending the class’s mission to bridge the two disciplines to benefit both physicists and artists in understanding and appreciating each other’s fields.
Balantekin says that the interdisciplinary course shows the rest of the campus community that physics is not just a technical subject. By demonstrating physics in a medium familiar to artists, it helps provide a new perspective and appreciation for the sciences. “If you’re a musician, it’s much better to learn about the physics behind how your instrument works, or the physics behind how colors mix. It’s more interesting, and then it still helps them to learn,” he says.
Design and performance of the prototype Schwarzschild-Couder telescope camera
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The debut of a new detector has many “firsts”: the first assembly, the first shift, the first light, the first detection… But if there’s one thing that makes a debut official—sort of like a detector’s birth certificate—it’s the detailed description of how the detector was built and how it performs.
And this is achieved in a new paper by members of the Cherenkov Telescope Array Consortium, published in the Journal of Astronomical Telescopes, Instruments and Systems. The paper documents the design of the camera of the prototype Schwarzschild-Couder Telescope (pSCT), a medium-sized candidate telescope for the Cherenkov Telescope Array (CTA). The paper also includes performance metrics that show its potential as a very-high-energy gamma-ray detector and that have already been used to plan an upgrade, a project which is now well underway. Very high energy gamma rays are the highest energy photons in the universe and can unveil the physics of extreme objects, including black holes and possibly dark matter.
The pSCT uses novel dual-mirror optics, rather than more traditional single-mirror optics, and relies on high-speed electronics to cover CTA’s middle energy range from 80 GeV to 50TeV. This camera was developed by a team spanning multiple universities and co-led by UW–Madison physics professor Justin Vandenbroucke, who has been working on this project since 2009.
