John S. Toll Endowed Lecture in Physics Honors a Culture of Excellence, Curiosity and Collaboration

 

John Toll (1923-2011) knew how to bring talented people together to build something bigger than themselves. 

As chair of the University of Maryland’s Department of Physics and Astronomy from 1953 to 1965, Toll recruited dozens of top-tier scientists to catapult the department onto an international stage. As president of UMD from 1978 to 1988 and founding chancellor of the University System of Maryland from 1988 to 1989, Toll helped grow the system and elevate its reputation. 

In 1990, faculty, staff and administrators of the department established an endowed professorship in his name, and in 2002, the physics building was named after Toll in recognition of his contributions to the university. 

Now, Chuan-Sheng Liu and Jingyi Liu are generously honoring Toll’s enormous legacy by endowing a lecture series in his name. The couple donated $50,000 to establish the John S. Toll Endowed Lecture in Physics, which will bring some of the brightest physicists to UMD’s campus to share their talent and enthusiasm with the community.

Chuan Liu is a professor emeritus of physics who joined UMD in 1974 and served as department chair from 1985 to 1990 and 1993 to 1994. His wife, Jingyi Liu (M.S. ’83, communications; Ph.D. ’91, radio/tv/film), was a cross-cultural communication consultant, educator and TV producer for educational programs, and she served as a contract interpreter for the U.S. Department of State.

The Lius’ gift to the university was followed by a $20,000 contribution from John Toll’s widow, Deborah Toll, who was thrilled to see her husband being honored in this way.

“I’m delighted that the Lius have established this lecture series, and it’s wonderful of them to do it in John’s name,” Toll said. “We now realize how sorely this country needs to improve scientific literacy, and I’m sure if John were alive, he would be doing something about it. If this lecture series can help bring some of the brightest minds to Maryland and get people excited about physics and science, all the better.”

The first John S. Toll Endowed Lecture in Physics was presented by S. James Gates Jr., then-president of the American Physical Society. He was the John S. Toll Professor of Physics from 1998 to 2017. Awarded the President’s National Medal of Science in 2011, Gates served on former President Barack Obama's Council of Advisors on Science and Technology. He is known among scJim Gates and John Toll in 2001.Jim Gates and John Toll in 2001.ientists for his work in supersymmetry, supergravity and superstring theory, and is more widely known by the public for his frequent appearances on scientific documentaries. Gates was the Ford Foundation Professor of Physics at Brown University and director of the Brown Theoretical Physics Center before returning to UMD in 2022.

“Gates is a great representative for this first lecture,” Chuan Liu said. “He is a brilliant physicist as well as a very accomplished leader and public speaker. In addition to bringing brilliant people to speak to the community, we want to embody the spirit of collaboration and curiosity that John brought, and I think Gates is a great example of this.”

The Lius stressed that John Toll was dedicated to bringing people together under the umbrella of science and knowledge. It was a core part of John Toll’s personality that they both experienced firsthand throughout the years they knew him.

“We got to know John Toll very well and consider him a good friend,” Chuan Liu said. “I first met him when he came back to Maryland as president of the university, but he was also a physicist, so we had a lot in common and we talked about physics often.”

The Lius were also involved in Toll’s efforts to build relationships with scientists in China. In 1979, soon after the normalization of U.S.-China relations, Chuan Liu and three physicists from Princeton were invited by the Chinese Academy of Sciences to visit the Institute of Plasma Physics in Anhui, China. It would be Chuan Liu’s first return trip to China since his family left the country for Taiwan in 1949, and he was very excited. 

When John Toll learned of the trip, he entrusted Chuan Liu to deliver a letter of invitation on behalf of Maryland Governor Harry Hughes to Wan Li, the governor of China’s Anhui province. Later that year, Wan led a delegation to visit Maryland, and Jingyi Liu served as interpreter for him and his delegation. While in Maryland, she got to know JChuan Sheng Liu and Jingyi Liu Chuan Sheng Liu and Jingyi Liu ohn Toll and Hughes and they encouraged her to come to UMD for her graduate studies.

The following year, Hughes visited Anhui province. Both John Toll and Chuan Liu were members of Hughes’ delegation. The exchange led to Maryland and Anhui becoming sister-states, which enabled numerous interactions and collaborations.

The Lius agree that part of John Toll’s ability to recruit talent and bring people together was his warmth and enthusiasm, qualities that seemed to come naturally to him. Deborah Toll echoed that sentiment, recalling stories her husband told about his early days as department chair.

“He used to bring some of the best scientists from all over the world to Maryland, and then he would take them to his mother’s house in Chevy Chase,” Toll explained. “She would host them and make meals for them. They had a grand time.”Deborah TollDeborah Toll

It was that kind of personal touch that the Lius remember so fondly. Although their gift reflects a deep appreciation and respect for John Toll as a leader and a scientist, it was his warmth and generosity as a friend that they often refer to when speaking about him. 

“We want to continue the culture of inclusion, excellence and curiosity that John established here,” Chuan Liu said. “He wanted to share the excitement of discovery and to really help spread the spirit of collaboration in science.”  

Perhaps no better example of that spirit is the Department of Physics’ traditional afternoon tea where students, faculty and staff came together daily to discuss science and socialize. John Toll started that tradition when he joined UMD in 1953, and it continued for many decades. 

“He was a person who respected people and tried to bring out their best with his inspirational leadership,” Chuan Liu said. “And he had a truly unselfish spirit that was dedicated to truth and to bigger things than himself. We want this wonderful culture that John Toll started to continue, and in naming this lecture series for John, we want the next generations to remember the older generations and know the history and traditions that were the foundation of the department.” 

Written by Kimbra Cutlip

Follow this link  to a 1989 profile of John S. Toll in the department's newsletter. 

John S. Toll Lecturers

Buonanno Receives Dirac Medal

Alessandra Buonanno has been awarded the Dirac Medal, along with Thibault Damour, Frans Pretorius, and Saul Teukolsky. The medal is given by the Abdus Salam International Centre for Theoretical Physics (ICTP), in Trieste, Italy, to honor significant contributions to theoretical physics. This year's recipients were cited for their work envisaging LIGO's detection of gravitational waves.

Buonanno is the director of the Astrophysical and Cosmological Relativity Department at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Potsdam and a Research Professor at the University of Maryland.

“It is a great honor for me to receive this prestigious award. It’s a wonderful recognition not only of my own research in gravitational waves, but of the work that the members of my research groups at the AEI and University of Maryland have done over many years,” Buonanno said. 

She joined the UMD Department of Physics in 2005, and received an Alfred P. Sloan Foundation Fellowship and the Richard A. Ferrell Distinguished Faculty Fellowship. She is a Fellow of the American Physical Society and the International Society of General Relativity and Gravitation. In 2018, she received the Leibniz Prize, Germany's prestigious research award. Earlier in 2021, she was elected to the U.S. National Academy of Sciences and was awarded the Galileo Galilei Medal of the National Institute for Nuclear Physics (INFN). Alessandra Buonanno © A. Klaer Alessandra Buonanno © A. Klaer Buonanno was also recently elected to the German National Academy of Sciences Leopoldina, which originated in 1652 as a classical scholarly society.

Buonanno's research has spanned several topics in gravitational-wave theory, data-analysis and cosmology. She is a Principal Investigator of the LIGO Scientific Collaboration, and her waveform modeling of cosmological events has been crucial in the experiment’s many successes.

Buonanno, Charlie Misner, Peter Shawhan and others detailed UMD's contributions to gravitational studies in a 2016 forum, A Celebration of Gravitational Waves

Sibylle Sampson, 1929-2021

Sibylle Sampson, a crucial member of the Department of Physics during a period of remarkable growth, died August 8 at the Ginger Cove retirement community in Annapolis.

SampsonJohn Toll praises Sibylle Sampson at her retirement party in 1991.John Toll praises Sibylle Sampson at her retirement party in 1991. joined the department in 1960 as a stenographer, and rose to become Director of Finance and the utterly essential aide to John Toll during his frenzied and fruitful expansion of UMD Physics. She was a renowned administrator and advocate of the department.

Toll’s arrival transformed the department (and by extension, elevated the research stature of the entire university). By all accounts, Sampson was immensely important, dedicated and effective in implementing Toll's plans.

Three decades ago, Sampson established the Sibylle Sampson Award  to highlight particularly innovative efforts of  physics staff members.

A native of Schwäbisch Gmünd, Germany, Sampson traveled to several countries for various jobs, and first arrived at College Park while visiting her brother, who was a postdoctoral researcher here. She eventually married her brother's roommate, an economics student, in 1959. Bob Sampson died just five months before Sibylle.

In retirement, both Sampsons enjoyed travel and boating. Sibylle was a poet in both English and German, and in 2018 published aSibylle Sampson recalls John Toll at his 2011 memorial.Sibylle Sampson recalls John Toll at his 2011 memorial. volume entitled, "Wanderings".   

Solstice

I woke into black silence,
The earth so still as if it held its
Spinning, had drowned
The breath of wind.

It is the night of darkest winter
Sol sistere – when the sun stands still,
When ancients built fires to
Chase the ghosts of night.

From the East,
Dawn slowly spreads her mantle,
Gray and reluctant first – her cloak will
Soon reveal a golden rim:

The promise of the sun
Of light embracing the earth,
Of snow vibrating in the spectrum of color -
The hope of every window in this world.

Sistere,
Stand still, o moment,
Remain.

 

New Approach to Information Transfer Reaches Quantum Speed Limit

Even though quantum computers are a young technology and aren’t yet ready for routine practical use, researchers have already been investigating the theoretical constraints that will bound quantum technologies. One of the things researchers have discovered is that there are limits to how quickly quantum information can race across any quantum device.

These speed limits are called Lieb-Robinson bounds, and, for several years, some of the bounds have taunted researchers: For certain tasks, there was a gap between the best speeds allowed by theory and the speeds possible with the best algorithms anyone had designed. It’s as though no car manufacturer could figure out how to make a model that reached the local highway limit.

But unlike speed limits on roadways, information speed limits can’t be ignored when you’re in a hurry—they are the inevitable results of the fundamental laws of physics. For any quantum task, there is a limit to how quickly interactions can make their influence felt (and thus transfer information) a certain distance away. The underlying rules define the best performance that is possible. In this way, information speed limits are more like the max score on an old school arcade game(link is external) than traffic laws, and achieving the ultimate score is an alluring prize for scientists.In a new quantum protocol, groups of quantum entangled qubits (red dots) recruit more qubits (blue dots) at each step to help rapidly move information from one spot to another. Since more qubits are involved at each step, the protocol creates a snowball effect that achieves the maximum information transfer speed allowed by theory. (Credit: Minh Tran/JQI)In a new quantum protocol, groups of quantum entangled qubits (red dots) recruit more qubits (blue dots) at each step to help rapidly move information from one spot to another. Since more qubits are involved at each step, the protocol creates a snowball effect that achieves the maximum information transfer speed allowed by theory. (Credit: Minh Tran/JQI)

Now a team of researchers, led by Adjunct Associate Professor Alexey Gorshkov, has found a quantum protocol that reaches the theoretical speed limits for certain quantum tasks. Their result provides new insight into designing optimal quantum algorithms and proves that there hasn’t been a lower, undiscovered limit thwarting attempts to make better designs. Gorshkov, who is also a Fellow of the Joint Quantum Institute, the Joint Center for Quantum Information and Computer Science (QuICS) and a physicist at the National Institute of Standards and Technology(link is external), and his colleagues presented their new protocol in a recent article published in the journal Physical Review X(link is external).

“This gap between maximum speeds and achievable speeds had been bugging us, because we didn't know whether it was the bound that was loose, or if we weren't smart enough to improve the protocol,” says Minh Tran, a JQI and QuICS graduate student who was the lead author on the article. “We actually weren't expecting this proposal to be this powerful. And we were trying a lot to improve the bound—turns out that wasn't possible. So, we’re excited about this result.”

Unsurprisingly, the theoretical speed limit for sending information in a quantum device (such as a quantum computer) depends on the device’s underlying structure. The new protocol is designed for quantum devices where the basic building blocks—qubits—influence each other even when they aren’t right next to each other. In particular, the team designed the protocol for qubits that have interactions that weaken as the distance between them grows. The new protocol works for a range of interactions that don’t weaken too rapidly, which covers the interactions in many practical building blocks of quantum technologies, including nitrogen-vacancy centers, Rydberg atoms, polar molecules and trapped ions.

Crucially, the protocol can transfer information contained in an unknown quantum state to a distant qubit, an essential feature for achieving many of the advantages promised by quantum computers. This limits the way information can be transferred and rules out some direct approaches, like just creating a copy of the information at the new location. (That requires knowing the quantum state you are transferring.)

In the new protocol, data stored on one qubit is shared with its neighbors, using a phenomenon called quantum entanglement. Then, since all those qubits help carry the information, they work together to spread it to other sets of qubits. Because more qubits are involved, they transfer the information even more quickly.

This process can be repeated to keep generating larger blocks of qubits that pass the information faster and faster. So instead of the straightforward method of qubits passing information one by one like a basketball team passing the ball down the court, the qubits are more like snowflakes that combine into a larger and more rapidly rolling snowball at each step. And the bigger the snowball, the more flakes stick with each revolution.

But that’s maybe where the similarities to snowballs end. Unlike a real snowball, the quantum collection can also unroll itself. The information is left on the distant qubit when the process runs in reverse, returning all the other qubits to their original states.

When the researchers analyzed the process, they found that the snowballing qubits speed along the information at the theoretical limits allowed by physics. Since the protocol reaches the previously proven limit, no future protocol should be able to surpass it.

“The new aspect is the way we entangle two blocks of qubits,” Tran says. “Previously, there was a protocol that entangled information into one block and then tried to merge the qubits from the second block into it one by one. But now because we also entangle the qubits in the second block before merging it into the first block, the enhancement will be greater.”

The protocol is the result of the team exploring the possibility of simultaneously moving information stored on multiple qubits. They realized that using blocks of qubits to move information would enhance a protocol’s speed.

“On the practical side, the protocol allows us to not only propagate information, but also entangle particles faster,” Tran says. “And we know that using entangled particles you can do a lot of interesting things like measuring and sensing with a higher accuracy. And moving information fast also means that you can process information faster. There's a lot of other bottlenecks in building quantum computers, but at least on the fundamental limits side, we know what's possible and what's not.”

In addition to the theoretical insights and possible technological applications, the team’s mathematical results also reveal new information about how large a quantum computation needs to be in order to simulate particles with interactions like those of the qubits in the new protocol. The researchers are hoping to explore the limits of other kinds of interactions and to explore additional aspects of the protocol such as how robust it is against noise disrupting the process.

Original story by Bailey Bedford: https://jqi.umd.edu/news/new-approach-information-transfer-reaches-quantum-speed-limit

In addition to Gorshkov and Tran, co-authors of the research paper include JQI and QuICS graduate student Abhinav Deshpande, JQI and QuICS graduate student Andrew Y. Guo, and University of Colorado Boulder Professor of Physics Andrew Lucas.