Superconductors finally prove quantum imaging effect predicted two decades ago

Dirk Morr, a physics professor at the University of Illinois Chicago (UIC), has developed a quantum imaging strategy that uses superconductors as tiny projectors. The research, published in Nature Physics, provides experimental support for an idea Morr first proposed two decades ago.Morr had been waiting for years to see whether his theoretical work could be demonstrated in an experiment. The recent findings showed quantum imaging similar to what his calculations had predicted.“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,” he said UIC Today reported.Morr joined the UIC faculty in 2001. As a theoretical physicist, he works with mathematical models to explain how nature behaves. He became interested in the possibility of quantum images after following an experiment at IBM that year.The IBM researchers used a scanning tunnelling microscope to arrange cobalt atoms into a small, elliptical structure called a quantum corral on a thin copper disc. The corral was about 20 nanometres long, making it thousands of times narrower than a strand of hair.Electrons behaving like wavesInside the corral, electrons in the copper behaved in an unusual way. Instead of acting only as individual particles, they formed waves.Morr compared the behaviour with ripples spreading across a pond after a stone hits the water. The ripples can move in different directions and have different intensities. In a similar way, the electrons inside the corral produced wave patterns.The observation was important because quantum mechanics shows that individual particles can display wave-like behaviour under certain conditions. Morr realised that these electron waves could potentially be used to create images, much like waves of light can be used to form an image.“But copper was not good enough to create high-resolution images, so we set out to investigate other materials,” said Morr.His work focused on superconductors. These are materials that can conduct energy without losing it. Morr's calculations showed that superconductors could potentially work like a lens, focusing quantum waves and producing high-resolution images.The idea could offer a way to study atoms without directly disturbing the original object being examined. In the quantum world, observing an object can change its properties, making direct observation difficult.“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.”A 20-year wait for the right experimentMorr's idea, however, could not be tested when he first developed it. The required experimental setup was not possible at the time because scientists could not make a quantum corral on a superconducting surface.The surface had to be extremely smooth and flawless for the experiment to work. According to Morr, that level of surface quality could not be achieved two decades ago.“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.The situation changed years later when researchers in Germany developed a setup that could test the idea. In 2023, Morr's colleagues at the University of Hamburg built a rectangular atomic corral on top of a superconductor.They then placed an iron atom inside the corral to generate a quantum-projected image. The experiment produced results that could be compared with Morr's theoretical prediction.The Hamburg setup was more complicated than the system Morr had originally imagined. To understand what the researchers were seeing, Chang Xu, a graduate student in Morr's group at UIC, created a theoretical multilayer model that reproduced the experimental arrangement.Model matched the quantum imageThe model included several layers. Niobium, a superconductor, formed the base. A silver island was placed in the middle, while an elliptical corral made from silver atoms was positioned on top.Xu's calculations showed quantum imaging that closely matched the effect observed by the Hamburg researchers. The result provided confirmation of Morr's prediction from 20 years earlier.The work also brought together theoretical and experimental research carried out by scientists in different countries. Morr said the result showed how collaboration between researchers can help move scientific ideas forward.“This study is a classic example of how scientists around the world collaborate and thus make progress happen,” Morr said.For Morr, the result also reflects two different reasons he finds science interesting. Sometimes, he said, his interest comes from the possible practical uses of a discovery. At other times, it comes from wanting to understand how nature works.“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.”

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