Quantum Solutions
Sitting in a high school classroom near the New York and Pennsylvania border in the early 1990s, Brian DeMarco became fascinated with questions that had once threatened to break the known world of physics. Questions like why hydrogen, the world’s simplest atom, cannot be fully understood without looking deep, deep inside its structure to reveal its probabilistic nature, which the physics of falling apples and planets cannot explain.
Those questions embody the study of quantum mechanics, and it’s been DeMarco’s life’s work for nearly 30 years. More than 20 of them have been spent at the University of Illinois where he is currently a professor of physics and director of the Illinois Quantum Information Science and Technology Center (IQUIST). Launched in 2018 within the Grainger College of Engineering, the interdisciplinary research center is dedicated to advancing quantum science for real-world applications.
DeMarco says the field of quantum physics is poised to transform technology as we know it over the next decade through quantum computing. This area of computer science will not only accelerate the work of scientists like DeMarco, but will touch every part of daily life, from cybersecurity to the creation of designer molecules and materials. And it’s all kicking off at Illinois.
“To me, it’s almost like a pre-Manhattan project or being in the room when the Internet was first created. This is a frontier of knowledge.”
—Brian DeMarco, U. of I. Professor, director of the Illinois Quantum Information Science and Technology Center (IQUIST)
“To me, it’s almost like a pre-Manhattan Project or being in the room when the internet was first created,” DeMarco says. “This is a frontier of knowledge.”
If classical physics is the study of the behaviors of observable objects—anything from atoms to planetary systems—quantum physics is the study of extremely small (i.e., subatomic) ones. However, because “large” objects like atoms are composed of “very small” particles (like subatomic quarks), all matter ultimately exists at the quantum level, if analyzed closely enough.
As “large” physical entities, we’re able to ignore the daily effects of quantum physics. This is, in part, because we experience only half of the physical forces that small quantum particles do, e.g., the gravity that holds us to the ground or the electromagnetism that runs our electronics.
These forces are well documented and can be reliably predicted using pre-fixed equations. For instance, if a ball’s exact height and velocity are known when it’s thrown into the air, an equation can predict exactly when and where it will fall.
By contrast, quantum physics is better understood through probabilities because the behavior of particles can change depending on how they’re interacted with or observed. The classic “Schrödinger’s cat” thought experiment illustrates this phenomenon: A cat is locked in a box with a poison that will be released if a radioactive atom in the box decays. Because radioactivity is a quantum process, the cat is both alive and dead until an observer opens the box to find out. Until then, the cat exists in a limbo state between the two possibilities.
Similarly, the state of quantum particles cannot always be accurately predicted in advance. This unpredictability results in properties such as superposition—a quantum system’s ability to be in multiple states at once—and entanglement, which describes the ability of quantum particles to instantaneously communicate with each other even when they’re miles apart.
So how do these properties translate to quantum computing? And how does it differ from conventional computing?
As it turns out, there are many similarities between the two, DeMarco says. Within a traditional computer, pieces of information are stored as bits that are contained within silicon transistors. These bits are represented by zeros and ones, and can be transformed by algorithms that channel them through a series of electrical circuits and logic decisions.
In this regard, a quantum computer is not that much different.
The principle of storing information in small, digital packages (i.e., bits) and transforming them through algorithms remains the same. However, quantum computers store that information in quantum bits, or “qubits.”
“Qubits can be zero or one, or kind of anywhere in between,” De-Marco explains. “They can encode more information because of that.”
Imagine a sphere, DeMarco suggests, where the north and south poles represent a zero and a one, respectively. A bit can only point directly north or directly south. But a qubit can point anywhere around the sphere. That’s because the qubit, as a quantum particle, can exist simultaneously as both a wave and a particle—which opens up new possible states of computer data storage. Qubits’ ability to encode more information, therefore, makes quantum computers a potentially powerful tool that can tackle complex problems.
But while conventional (i.e., binary) computers are a mature technology, quantum computers are still very much in their infancy. So much so, that there is no consensus on how to build one, DeMarco says.
Even deciding what to use as a qubit is an open question. Top contenders include particles of light called photons and trapped ions (which use magnetic and electrical fields to “trap” charged particles). Both options are being explored by IQUIST researchers.
Qubits also are much more sensitive than binary bits and can be easily damaged. “The biggest technical challenge in developing quantum computers is preventing noise from disrupting the computation, whether its thermal, electromagnetic or mechanical,” says Eric Chitambar, U. of I. associate professor of electrical and computer engineering. “The noise will perturb the system,” he explains, resulting in the loss of a qubit’s wave-like properties. To shield qubits from disturbances, quantum-computer prototypes are run at very low temperatures, near -459°F, Chitambar says.
Meanwhile, Elizabeth Gold-schmidt, U. of I. assistant professor of physics and an IQUIST member, is attempting to solve the disturbance problem by encoding qubits in single photons of light.
The advantage of photons is that they keep the qubit “well isolated from its environment, so we can keep it coherent and stable as it transmits,” Goldschmidt says. “And all these things are great, [but] processing quantum information with light is very, very hard.”
In addition, quantum-computer researchers are still seeking the equivalent of a binary computer’s silicon transistors, which flip electrical currents to represent either zeros or ones.
“Every quantum computer that exists today is effectively a physics experiment,” Goldschmidt says. “People around the world are attempting to build quantum computers based on wildly divergent physical hardware, making different sets of choices and tradeoffs surrounding the need for simultaneous isolation and control.”
So then, how can a quantum computer be programmed? Those answers are being sought by research scientists at the U. of I.’s National Center for Supercom-puting Applications (NCSA).
“To program for a quantum computer today, we have to know a great deal of hardware details,” says Bruno Abreu, a former U. of I. scientist who is now deputy scientific director of the Pittsburgh Super-computing Center. “That’s a big challenge. We’re trying to come up with solutions that abstract those details away … so that people can think about the algorithms and operations without [having to] think about the hardware.”
Technological and programming challenges aside, Goldschmidt is confident that “quantum computers are likely to change the world.”
As one example, quantum computing is expected to transform cybersecurity. If an organization uses quantum technologies, “someone attempting to break into your quantum system has to make a basis choice,” Goldschmidt says, meaning that hackers must predict what they’re about to observe.
“Every quantum computer that exists today is effectively a physics experiment. People around the world are attempting to build quantum computers based on wildly divergent choices and tradeoffs.”
—Elizabeth Goldschmidt, U. of I. Assistant Professor, Member of the Illinois Quantum Information Science and Technology Center
“Unless they know what choice you’re making, they won’t be able to get the same information,” she says. However, she also notes that even if a hacker makes the wrong assumption about the quantum state they’re observing, they could still destroy unrecoverable information in the process.
Meanwhile, Chitambar is exploring how entangled qubits can be used to communicate more efficiently and securely. Those discoveries could have applications for secure “secret sharing,” he says, drawing an analogy between quantum entanglement and multiple launch keys for nuclear-armed ballistic missiles.
Beyond cybersecurity, quantum computers will likely excel at factoring large numbers, simulating physical systems, searching databases and resolving optimization problems. “These problems have a particular mathematical structure that enables them to be solved faster on a quantum computer,” Chitambar says.
While such applications might not sound exciting, they do have important implications. For example, a quantum computer’s ability to factor large numbers faster than a binary computer could put traditional encryption methods at risk, DeMarco says, resulting in the need for quantum-enabled encryption to defend against quantum-enabled hackers.
In more proactive applications, quantum computing’s ability to simulate physical systems could radically transform a range of fields. “Right now, we rely on approximate models for everything from semiconductors to pharmaceuticals,” Goldschmidt says. “Sufficiently large and high-fidelity quantum computers would allow dramatic breakthroughs in our ability to understand and then design materials and molecules for medicine, energy generation and storage—and likely much more beyond what we can envision today.”
While quantum computers hold significant promise, they won’t fulfill all of our computing requirements. “Not all problems have a structure [suitable for quantum computers],” Chitambar says. Consequently, binary computers will still be needed.
For example, DeMarco says, it’s highly unlikely you’ll have a quantum laptop computer. Instead, quantum computers likely will be housed in large computing centers and used in ways similar to today’s supercomputers.
There’s no crystal ball for predicting where the next decade of quantum research will lead, but DeMarco is optimistic that even though a true quantum future is far off, utility prototypes will likely emerge in the next five to seven years—in no small part due to the groundbreaking work underway at Illinois.
Interdisciplinary research
An integral part of U. of I.’s culture
Although researchers like Elizabeth Goldschmid and Eric Chitambar are working on related topics under the IQUIST umbrella, they’re doing so from entirely separate scientific perspectives. In fact, IQUIST members come from a wide spectrum of disciplines.
That’s not a random occurrence. “At Illinois, interdisciplinary or convergent research is part of our DNA,” explains Susan Martinis, MS ’88 LAS, PHD ’90 LAS, the university’s vice chancellor for research and innovation.
As a U. of I. graduate student in the 1980s, Martinis witnessed that convergence firsthand when Illinois’ Beckman Institute for Advanced Science and Technology brought biologists, psychologists and engineers into the same building to collaborate.
Interdisciplinary research is particularly essential for fields like quantum science, in which no one discipline has all of the answers yet, says Bruno Abreu, a former U. of I. scientist who is now deputy scientific director of the Pittsburgh Supercomputing Center. “It’s key to have people with different expertise—like physicists working to understand quantum information science at a very basic level; computer scientists thinking about algorithms; and electrical engineers [thinking about] control systems.” —S.W.
Quantum Ecosystem
The Chicago Quantum Exchange brings Midwest universities and federal labs together to spark innovation
As much as U. OF I. researchers benefit from interdisciplinary quantum research, they also benefit from—and contribute to—a quantum ecosystem that is driving statewide innovation.
That ecosystem emerged in part through the formation of the Chicago Quantum Exchange (CQE) in 2017, which brought together multiple Midwest universities, including the U. of I., University of Chicago, University of Wisconsin–Madison and Purdue University, along with such scientific research facilities as Fermilab and Argonne National Laboratory, to focus on advancing quantum research and the quantum economy. In 2021, the group formed the Duality Quantum Accelerator to provide business training and support to quantum startups in the region. The U. of I.’s vice chancellor for research and innovation, Susan Martinis, is vice chair of Duality’s governing board.
Further enriching Illinois’ quantum ecosystem is P33 Chicago, a nonprofit committed to inclusively growing Chicagoland’s tech sector.
“We’re a bit of a utility player,” explains Meera Raja, ’03 LAS, senior vice president of deep tech at P33 Chicago. “We can be connectors, executors, thought partners.” The organization works to ensure “that what everyone’s doing complements each other,” she says. P33 Chicago’s activities can range from tracking university work to connecting with businesses to learn what kinds of incentives they need to consider adopting new technologies.
At the same time, Illinois Gov. J.B. Pritzker has been pivotal in bringing quantum-technology funding to the state through the Innovate Illinois coalition. Launched in 2023, the coalition works to secure federal and private investments in science, technology and climate initiatives. —S.W.
DARPA and the U. of I.
Partnership seeks to establish a “Quantum Proving Ground”
Despite the strides that the U. of I. has already made in quantum research, its work has just begun, DeMarco says. To that end, the university, Illinois Gov. J.B. Pritzker and the U.S. Dept. of Defense’s Defense Advanced Research Projects Agency (DARPA) announced a new partnership
in July 2024 that will create a Quantum Proving Ground (QPG) to identify promising quantum technologies and bring them to utility scale.
Planning for a QPG began in DeMarco’s university office after DARPA officials approached him and Harley Johnson, associate dean for research in the Grainger College of Engineering, with the idea.
“What utility scale means is that a company like Bank of America would pay to use a big quantum computer because it’s useful to them,” DeMarco explains.
DARPA and other agencies will provide federal funding, and Pritzker and the State of Illinois have pledged to co-invest up to $140 million in the QPG.
In addition to the QPG, Pritzker has announced plans to build the Illinois Quantum and Microelectronics Park, a quantum-focused research and development campus in Chicago. Johnson has been named the campus’ director.
“The Illinois Quantum and Microelectronics Park is poised to have an enormous impact in Illinois, across the nation, and around the world,” Johnson says. “We are proud to have been called on to lead the effort, and I’m personally thrilled to have an opportunity to help shape this historic project. We have a once-in-a-generation opportunity to make the world better through advancements in quantum computing and microelectronics.”
Quantum startup PsiQuantum will be the Park’s first tenant; its engineers and scientists will work on building the first utility-scale quantum computer.
While these new projects will have national and even worldwide significance, they also will be meaningful to many U. of I. students and faculty, DeMarco says. Rather than allocating all of the QPG’s funding to a single promising technology, the funding will likely be parceled to support different aspects of the project, such as the design of testing methods to determine if a quantum technology can reach utility scale, DeMarco says.
“It’s an opportunity for our researchers and students to contribute to the technology of the future,” he says. —S.W.