‘It takes a village to trap an ion’: A look inside the Duke Quantum Center - The Duke Chronicle

As Duke has spent the past years publicly investing in and debating artificial intelligence, the University has simultaneously focused on an entirely different form of technological innovation: quantum computing.

The Duke Quantum Center (DQC), located in downtown Durham in the Chesterfield building, is the only “vertical” quantum computing center in the entire world. The center — led by Kenneth Brown, Michael J. Fitzpatrick distinguished professor of engineering — is the brainchild of leading quantum scientists at Duke. Principally, the center has the unique capability to create a quantum computer from programming to assembly. Brown co-founded the center in 2021, alongside several other experts, and assumed the position of director in 2026. Under his leadership, the center has strengthened ties to Duke’s Deep Tech, the University of North Carolina at Chapel Hill and North Carolina State University and its researchers have started to earn accolades. Brown said his “long-term dream” for the center is to move it out of central Durham and onto the Duke campus, so that undergraduates can interact with it more often.

Amy Zhang Scientists working at the Duke Quantum Center. Quantum computing at a glance Quantum computing represents an alternative to digital computing — the current standard for the world’s devices. Almost all devices, from most supercomputers to the iPhone, are digital: they encode information in bits, which take on the value 0 or 1. Even if a digital computation works quickly, the process ultimately requires solving a complex computational problem by following pre-defined logical steps until one works, or essentially approximating the problem to find a sufficient solution. The method works effectively for daily tasks, but can be insufficient for cutting-edge research involving heavy computation. By contrast, quantum computers rely on quantum bits, known as qubits, which can be put into superpositions of quantum states: both 0 and 1 at the same time. This mixture underlies the potential of quantum computers. If engineered a certain way, a quantum computer solves a problem by amplifying the correct solutions and dampening the incorrect ones, possibly computing in seconds what may have taken a classical computer millennia. Or at least, in theory. Brown described the quantum mechanical effect as “subtle” and could easily fall apart with “noise” — in other words, the components of an environment that dampen the correct solutions. “Until the beginning of the 20th century, human beings had been around a long, long time and never noticed anything quantum mechanical,” Brown said.

Amy Zhang Optics and electronics for stabilizing the frequency of the lasers used for manipulating barium ions at the Duke Quantum Center. But then, scientists began to achieve “sufficiently precise measurement of things” and “run into real physics mysteries” that could only be answered with quantum mechanics. These answers, along with the properties that DQC seek to exploit, are so elusive that science did not notice them until the early 1900s. Di Fang, associate professor of mathematics and a faculty member of DQC, compared the current state of quantum computing to being able to play a sheet of music, but only on a toy piano. “There are already many things you can do with it,” Fang said. But ... in order to play Mozart, we hope to have a full piano.” However, Fang said the “toy piano” stage is still better than where quantum computing was around a decade ago. Then, quantum algorithms were well known, yet no one had a quantum computer to execute them, as if piano pieces were written before pianos were even invented. In the meantime, Fang, alongside other faculty members and students at DQC, are still forging ahead, writing new and grander pieces through innovative technology. Current projects Alice, Bob and Cleo are a chatty trio, sending hundreds of messages to each other per second. But they are not a circle of friends in a group chat. Instead, they are a set of hulking machines, specifically trapped-ion quantum computers, built for data transmission experiments. Each machine weighs hundreds of pounds and is usually hidden under cloaks in a shared computational room. Ashish Kalakuntla, a doctoral candidate studying physics, explained that Alice, Bob and Cleo communicate with one another via barium or ytterbium lasers. Both methods can prove effective in blocking out the noise that makes quantum computing less effective. Two or more of the computers, or “traps,” shoot photons at one another through an optical fiber, entangling them and allowing them to communicate. Photons, or physical light signals, represent an easier method of communicating qubits from one machine to another. According to Kalakuntla, the trio once achieved a 97% fidelity rate, meaning they entangled 250 photon pairs per second. Typically, photons encounter one another less than 2% of the time. Only a constant bombardment of photons compensates for these difficult odds. Although other researchers have worked on similar technology, the DQC’s development of the three-machine trapped-ion network marks an unprecedented achievement in the quantum computing world. Even some of the most prestigious labs working on networks have only one or two traps. Brenton Wang "Cleo," a trapped-ion quantum computer. But, DQC has more than just Alice, Bob and Cleo. Emma Stavropoulos, a physics doctoral candidate, said that many Duke community members may not realize the different expertise required for the experiments done at DQC. “We have people working on theory, lasers and optics, radiofrequency engineering, electronics, chip design and fabrication, cryogenic systems, noise and stability, and control software,” Stravropoulos said, as examples. Stavropoulos has been working on a project around quantum simulation, or QSIM. QSIM is a quantum analog simulator that helps solve Hamiltonian systems, which provide instructions for quantum computers. The Hamiltonian problems she aims to solve involve dozens of particles bouncing against one another, each with a unique velocity and acceleration. The particles can overwhelm a classical computer, causing it to fail or produce incorrect results. The usage of the Hamiltonian system allows a “high degree of control,” according to Stavropoulos. The experiments she and her team conduct to improve the length and coherence of simulations help further enhance already uniquely powerful computer systems. Brenton Wang A maze of lasers, at the center of QSIM. Looking forward DQC, which started with five faculty members in 2021 and has since grown to 15, has already attracted quantum theorists from around the country. Fang said the center was one of the main reasons she took a position at Duke. “The interdisciplinary aspect of Duke is amazing,” Fang said. “...

The Duke Quantum Center is really unique in that regard.” Ian Von Wald, program director at DQC, said the center aims to further grow its community through creating a fund for graduate students, hosting talks and reintroducing a summer school for people interested in quantum computing. As Stavropoulos put it, “it takes a village to trap an ion.” Amy Zhang Microfabricated trap for holding atomic ions at the Duke Quantum Center (credit: Sandia National Laboratories). Beyond community-building, the center still aims to make greater contributions to the field beyond its existing breakthroughs. For example, the center is working toward creating a 256-qubit quantum computer within seven years, and received a $1 million grant for the project in 2024. Once completed, the quantum computer would be the most powerful of its kind. Brown said he looks forward to venturing into uncharted territory with this new computer, which he anticipates will be so powerful that it can perform tasks that no classical computer can. Someday, quantum computing could yield advances in drug discovery, digital privacy or solar panel technology, and perhaps even daily uses for an average person. Fang stressed caution, noting that the center may not be the lab to make a quantum breakthrough. Public and private labs worldwide are pursuing different types of quantum computers, and the center is currently pursuing only the trapped ion approach, one method of many. Perhaps the breakthrough quantum computer will be forged through a different method from a superconducting qubit to a photonic qubit or quantum dot to neutral atom — “it’s unclear at this moment,” Fang said. But maybe, according to Fang, “everyone has their own style of piano."