UIC physicist cracks the code to create quantum images

Dirk Morr, a physics professor in the College of Liberal Arts and Sciences, has developed a quantum imaging strategy that uses superconductors (materials that conduct energy without losing any) like tiny projectors. His research appears in Nature Physics.

Morr's discovery was a long time coming - he'd been waiting to prove it for 20 years.

"I don't know if 'blessed' is the right word, but it's a very cool accomplishment," Morr said. "It feels rewarding to have theorized something two decades ago and finally see it come to fruition. That's what science is all about."

A theoretical physicist, Morr has always enjoyed explaining nature with mathematical models.

"Experimental physicists provide clues, and then theoretical physicists like me put together theories that explain what we see all around us," he said.

Morr joined the UIC faculty in 2001. That year, he was paying close attention to an experiment underway at IBM. Using a scanning tunneling microscope, the researchers there arranged a small, elliptical "corral" of cobalt atoms on top of a thin copper disc. The corral was 20 nanometers long, thousands of times narrower than a strand of hair.

The copper electrons in the corral responded strangely: They formed waves.

"Imagine a shallow pond that's been disturbed by a stone. Waves begin to ripple in different intensities and directions," Morr said.

The electrons demonstrated that under certain conditions, individual particles can behave like waves: a key concept in quantum mechanics. And just like waves of light, Morr said, the copper waves could be used to create images.

"But copper was not good enough to create high-resolution images, so we set out to investigate other materials," said Morr.

Specifically, superconductors. Like a lens focuses visible light onto a screen, Morr demonstrated that superconductors could theoretically project high-resolution quantum images, with which researchers could study atoms with more nuance than ever before.

"In the quantum world of atoms, if you look at an object, you actually change its properties," Morr said. "Imagine that every time you look at a book lying on a table, the book falls off the table. But if I can create an image of the atom, then I can study the image without perturbing the original."

Unfortunately, Morr's hypothesis came 20 years ahead of its time.

"Back then, you couldn't construct a quantum corral on top of a superconducting surface. The surface of the superconductor would need to be completely smooth and flawless, which just wasn't possible," he said.

Years later, a discovery 4,000 miles away suggested otherwise.

In 2023, Morr's colleagues at the University of Hamburg in Germany built a rectangular atomic corral on top of a superconductor. They tested Morr's hypothesis by placing an iron atom in the corral to generate a quantum-projected image.

However, the Hamburg team's experimental setup was more complicated than what Morr envisioned 20 years ago. Chang Xu, a graduate student in Morr's group at UIC, developed a theoretical, multilayer model mirroring the Hamburg researchers' setup: The superconductor niobium formed the base, with a silver island in the middle and an elliptical corral of silver atoms on top.

Xu's model revealed quantum imaging very similar to that observed by the Hamburg group, confirming Morr's prediction from 20 years earlier.

"This study is a classic example of how scientists around the world collaborate and thus make progress happen," Morr said.

"There are many reasons I'm intrigued by science. At times, I focus on the practical applications of a discovery; at others, I'm motivated by intellectual curiosity and a sense of wonder of how beautiful and complex nature is," he said. "In this case, I am both."