Recent Alumnus Zachary Eldredge Studies Solar Energy as ORISE Fellow

As a student, Zachary Eldredge (Ph.D. ’19, physics) examined the use of quantum mechanics to improve measurements.

“If you nEldredge 2020Zach Eldredge. Photo by Faye Levine.eed to know the difference in some quantity between two points, a common method is to measure the quantity at each point and then subtract,” Eldredge explained. “Instead, we developed methods to measure the difference directly. Our methods are more accurate because we only measure once, not twice.”

After graduating last May, Eldredge took this expertise and his strong physics foundation to the Department of Energy’s Solar Technologies Office, which aims to make solar energy less expensive and more accessible and increase the amount of renewable energy in the United States. He spent seven months working in the office as an Oak Ridge Institute for Science and Education (ORISE) Fellow and is now a technology manager.

“The process of how technologies progress from lab science to usable products is really interesting to me and was important to my quantum research, as quantum technology is trying to make that same leap at the moment,” he said. “In addition, physics has been a wonderful foundation. A good physics education prepares you to pick out the relevant patterns and generalize knowledge really quickly, and it's been a great help in giving me the background to get up to speed on all kinds of other technologies.”

Eldredge knew early on in his studies that he was interested in finding a science policy job to align with his interests in climate, renewable energy and technology development. 

“I really wanted to shift gears from my academic work into something more climate focused, and the ORISE fellowship provided a great opportunity.”

During his time at Maryland, Eldredge co-authored nine publications, including three first-author papers published in the journals Physical Review A and Physical Review Letters. 

“I’m proud to say that two of Zach’s papers are the highlights of my own research over the past few years,” said Alexey Gorshkov, Eldredge’s advisor who is an adjunct associate professor in the Department of Physics and a physicist at the National Institute of Standards and Technology. “In fact, these two papers are so promising that we filed patents for the corresponding ideas, all having to do with the harnessing of the peculiarities of quantum mechanics for technologies such as powerful computing, secure communication and superior sensing.”

In addition to his work in the lab, Eldredge served as president of the social activism group Science for the People UMD and as a member of the Graduate Student Government. 

“Not only is Zach an excellent physicist, he was also an excellent citizen of the department,” said Steve Rolston, professor of physics and department chair. “He was one of the most active members of our self-organized graduate student committee, which strives to make graduate school as positive an experience as possible.” 

Eldredge also participated in public outreach activities, such as the American Physical Society’s Congressional Visits Day, the USA Science & Engineering Festival, and UMD’s Maryland Day. 

“I felt I had a duty as a publicly funded scientist at a major public university to reach out and talk to people, because the knowledge I gained there belongs to everyone,” Eldredge said. “When we discover amazing things, it is on us to communicate about them to the public.”

Written by Chelsea Torres

Fifth Edition of “Exploring Quantum Physics” to Launch on Coursera

Charles Clark and Victor Galitski will launch the fifth edition of their Coursera class on quantum physics Jan. 20, 2020. Alireza Parhizkar, a UMD graduate student will serve as teaching assistant.

“The course begins by establishing the conceptual grounds of quantum mechanics and promises an exciting journey,” says Parhizkar, who joined Galitski’s research group in the summer of 2019. “It fulfills this promise by immersing the learner in advanced subjects of quantum physics, like superconductivity and path integrals, and illustrating them with colorful exercises.”   coursera cats bannerTwo JQI Fellows will launch the fifth edition of "Exploring Quantum Physics" on Coursera Jan. 20. (Credit: Anna Bogatin)

The free course, titled “Exploring Quantum Physics,” explains topics in quantum physics at a level appropriate for an advanced undergraduate or beginning graduate student. The previous four editions had a total of about 100,000 enrollees, with roughly 2,000 people completing the course. “That’s a good number for a massive open online course, or MOOC,” says Clark, who is an Adjunct Professor of Physics, a Fellow of the Joint Quantum Institute (JQI), and a Fellow at the National Institute of Standards and Technology in Gaithersburg, Maryland. Clark adds that the new edition of the course has a revised grading system as well as updated homework and exam questions.

“Exploring Quantum Physics” consists of eight weeks of video lectures, with a number of five- to fifteen-minute videos per week. The videos include voluntary ungraded quizzes, which automatically pause the presentation so that students have an opportunity to answer relevant questions. There are also weekly homework assignments—some will include reading historical papers by influential early quantum scientists such as Albert Einstein and Niels Bohr—as well as a final exam. “We tried to strike a balance between providing a historical perspective on the early development of quantum physics and modern concepts,says Galitski, who holds the Chesapeake Chair of Theoretical Physics at the University of Maryland (UMD).

An advantage of MOOCs is that the course material is available to anyone, including some students who are younger than traditional undergraduates. Khadija Niazi and her twin brother Muhammad, who grew up in Pakistan, were 13 years old when they enrolled in an earlier edition of the course. Khadija, who once spoke about her experience with MOOCs at the World Economic Forum, says that she “thoroughly enjoyed that course [e]specially because of the peer's help and Charles Clark's constant help and encouragement in the forums.” Before beginning the quantum physics course, the twins had completed some introductory physics classes on the site and learned some calculus from videos on YouTube. Muhammad says that they wanted “to get a taste of what lies ahead.”

Both Niazi siblings stayed in contact with Clark after completing the class. Muhammad, who went on to publish his first experimental physics paper in the journal Royal Society Open Science when he was 16, says he will probably take the new edition of the course to solidify his understanding of the content.

Michael Winer, a physics graduate student at UMD, took an earlier edition of the course when he was a 10th grader at Montgomery Blair High School in Silver Spring, Maryland because he hoped to do physics research over the summer. “By far the greatest thing that came out of my taking the course was that I contacted professor Galitski and did research with him for two summers,” Winer says. “This was my first real research experience, and taught me a lot about the scientific process.” That work led Winer to win the Intel Science Talent Search competition in 2015, earning him a prize of $150,000 and a meeting with President Obama.

“Exploring Quantum Physics” is now open for enrollment. To learn more about the course and to see a detailed syllabus, please visit the landing page at Coursera.

Original story by by Jillian Kunze

Galactic Gamma-ray Source Map Reveals Birthplaces of High-energy Particles

Nine sources of extremely high-energy gamma rays have been identified in a new catalog compiled by researchers with the High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, including nine University of Maryland physicists. All nine sources produce gamma rays with energies over 56 trillion electron volts (TeV)—more than eight times the energy of the most powerful proton beams produced at particle accelerators on Earth—and three emit gamma rays extending to 100 TeV and beyond, making these the highest-energy sources ever observed in our galaxy. The catalog helps to explain where the particles originate and how they are produced with such extreme energies.hawc 2020The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory was used to create a map of the galactic plane indicating the highest energy gamma ray sources yet discovered. (Credit: Jordan Goodman/University of Maryland)

“The very high-energy gamma rays we detect are produced by interactions of even higher energy charged particles near their source,” said Jordan Goodman, a Distinguished University Professor of Physics at UMD and U.S. lead investigator and spokesperson for the HAWC collaboration.  “Charged particles are bent in the magnetic fields of our galaxy and don’t point back to their origin. Gamma rays, like light, travel in straight lines allowing us to use them to map the sources of the high-energy emission. HAWC, which is a wide field-of-view instrument, views the overhead sky 24/7 giving us a deep exposure to look for the rare high energy gamma ray events.”

The catalog of high-energy sources was published online in the journal Physical Review Letters on Jan. 15, 2020.  Higher-energy astrophysical particles have previously been detected, but this is the first time specific galactic sources have been pinpointed for such high-energy particles. All of the sources have extremely energetic pulsars nearby. The number of sources detected may indicate that ultra-high-energy emission is a generic feature of powerful particle winds coming from pulsars embedded in interstellar gas clouds known as nebulae, and that more detections will be forthcoming.

The HAWC Gamma-Ray Observatory consists of an array of water-filled tanks sitting high on the slopes of the Sierra Negra volcano in Puebla, Mexico, where the atmosphere is thin and offers better conditions for observing gamma rays. When gamma rays strike molecules in the atmosphere they produce showers of energetic particles. Nothing can travel faster than the speed of light in a vacuum, but in water light moves a little slower. As a result, some particles in cosmic ray showers travel faster than light in the water inside the HAWC detector tanks. The faster-than-light particles, in turn, produce characteristic flashes of light called Cherenkov radiation. Using recordings of the Cherenkov flashes in the HAWC water tanks, researchers reconstruct the sources of particle showers and learn about the particles that caused them.

The HAWC collaborators plan to continue searching for the sources of high-energy cosmic rays. By combining their data with measurements from other types of observatories, such as neutrino, X-ray, radio and optical telescopes, they hope to elucidate the astrophysical mechanisms that produce the cosmic rays that continuously rain down on our planet.

“There are still many unanswered questions about cosmic-ray origins and acceleration,” said Kelly Malone, an astrophysicist in the Neutron Science and Technology group at Los Alamos National Laboratory and a member of the HAWC scientific collaboration. “High energy gamma rays are produced near cosmic-ray sites and can be used to probe cosmic-ray acceleration. However, there is some ambiguity in using gamma rays to study this, as high-energy gamma rays can also be produced via other mechanisms, such as lower-energy photons scattering off of electrons, which commonly occurs near pulsars.”


In addition to Goodman, other UMD co-authors from the Department of Physics included Visiting Professor Robert Ellsworth; Principal Engineer Michael Schneider; Research Scientist Andrew James Smith; Graduate Students Kristi Engel and Elijah Job Tabachnick; and Postdoctoral Associates Colas Rivière, Chad Brisbois and Israel Martinez-Castellanos.

Text for this news item was adapted with permission from a press release written by Los Alamos National Laboratory. 

The paper “Multiple Galactic Sources with Emission Above 56 TeV Detected by HAWC,” A.U. Abeysekara, et al. was published in Physical Review Letters on January 15, 2020.

The National Science Foundation, the U.S. Department of Energy and Los Alamos National Laboratory provided funding for the United States’ participation in the HAWC project. The Consejo Nacional de Ciencia y Tecnología (CONACyT) is the primary funder for Mexican participation. The content of this article does not necessarily reflect the views of these organizations.  

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


Remote Quantum Systems Produce Interfering Photons

UMD physicists have observed, for the first time, interference between particles of light created using a trapped ion and a collection of neutral atoms. Their results could be an essential step toward the realization of a distributed network of quantum computers capable of processing information in novel ways.

In the new experiment, atoms in neighboring buildings produced photons—the quantum particles of light—in two distinct ways. Several hundred feet of optical cables then brought the photons together, and the research team, which included scientists from the Joint Quantum Institute (JQI) as well as the Army Research Lab, measured a telltale interference pattern. It was the first time that photons from these two particular quantum systems were manipulated into having the same wavelength, energy and polarization—a feat that made the particles indistinguishable. The result, which may prove vital for communicating over quantum networks of the future, was published recently in the journal Physical Review Letters.

“If we want to build a quantum internet, we need to be able to connect nodes of different types and functions,” says JQI Fellow Steve Rolston, a co-author of the paper and a professor of physics at the University of Maryland. “Quantum interference between photons generated by the different systems is necessary to eventually entangle the nodes, making the network truly quantum.”photon interference diagram v5 hires 002A schematic showing the paths taken by photons from two different sources in neighboring buildings. (Credit: S. Kelley/NIST)

The first source of photons was a single trapped ion—an atom that is missing an electron—held in place by electric fields. Collections of these ions, trapped in a chain, are leading candidates for the construction of quantum computers due to their long lifetimes and ease of control. The second source of photons was a collection of very cold atoms, still in possession of all their electrons. These uncharged, or neutral, atomic ensembles are excellent interfaces between light and matter, as they easily convert photons into atomic excitations and vice versa. The photons produced by each of these two systems are typically different, limiting their ability to work together.

In one building, researchers used a laser to excite a trapped barium ion to a higher energy. When it transitioned back to a lower energy, it emitted a photon at a known wavelength but in a random direction. When scientists captured a photon, they stretched its wavelength to match photons from the other source.

In an adjacent building, a cloud of tens of thousands of neutral rubidium atoms generated the photons. Lasers were again used to pump up the energy of these atoms, and that procedure imprinted a single excitation across the whole cloud through a phenomenon called the Rydberg blockade. When the excitation shed its energy as photons, they traveled in a well-defined direction, making it easy for researchers to collect them.

The team used an interferometer to measure the degree to which two photons were identical. A single photon entering the interferometer is equally likely to take either of two possible exits. And two distinguishable photons entering the interferometer at the same time don’t notice each other, acting like two independent single photons.

But when researchers brought together the photons from their two sources, they almost always took the same exit—a result of quantum interference and an indication that they were nearly identical. This was precisely what the research team had hoped for: the first demonstration of interference between photons from these two very different quantum systems.

In this experiment, photons traveled from the first building to the second via hundreds of feet of optical fiber. Due to this distance, sending photons from both systems to meet at the interferometer simultaneously was a feat of precise timing. Detectors were placed at the exits of the interferometer to detect where the photons came out, but the team often had to wait—gathering all the data took 24 hours over a period of 3 days.

Further experimental upgrades could be used to generate a special quantum connection called entanglement between the ion and the neutral atoms. In entanglement, two quantum objects become so closely linked that the results from measuring one are correlated with the results from measuring the other, even if the objects are separated by a huge distance. Entanglement is necessary for the speedy algorithms that scientists hope to run on quantum computers in the future.

Generating entanglement between different quantum systems usually requires identical photons, which the researchers were able to create. Unfortunately, trapped ions emit photons in a random direction, making the probability of catching them low. This meant that only about eight photons from the trapped ion made it to the interferometer each second. If the researchers attempted to perform more intricate experiments with that rate, the data could take months to collect. However, future work may increase how frequently the ion emits photons and allow for a useful rate of entanglement production.  

“This is a stepping-stone on the way to being able to entangle these two systems,” says Alexander Craddock, a graduate student at JQI and the lead author of this study. “And that would be fantastic, because you can then take advantage of all the different weird and wonderful properties of both of them.”

Story by Jillian Kunze

In addition to Rolston and Craddock, co-authors of the paper include JQI graduate students John Hannegan, Dalia Ornelas-Huerta, and Andrew Hachtel, JQI postdoctoral researcher James Siverns, Army Research Laboratory scientists and JQI Affiliates Elizabeth Goldschmidt (now an Assistant Professor of Physics at the University of Illinois) and Qudsia Quraishi, and JQI Fellow Trey Porto.

Research Contact
Steve Rolston
This email address is being protected from spambots. You need JavaScript enabled to view it.