Scientists Develop New X-Ray Technique To Watch Quantum Materials Respond To Laser Pulses
New imaging method offers scientists an unprecedented view inside silicon carbide as researchers work toward precisely engineering future quantum devices
Researchers use the Advanced Photon Source to watch, in unprecedented detail, how laser energy moves through silicon carbide — a key step toward manufacturing quantum devices with atomic precision.
Key takeaways
- Argonne scientists have developed a new X-ray imaging technique that captures, in three dimensions and in real time, how silicon carbide responds after an ultrafast laser pulse.
- The technique revealed two energy-transport processes inside the crystal: a rapid mechanical wave and slower heat-driven atomic vibrations.
- These insights could help researchers place quantum defects more precisely, supporting the development of reliable quantum devices and manufacturing methods.
Creating a quantum device often begins by intentionally damaging a crystal.
Scientists fire an ultrafast laser pulse into a material, knocking atoms out of place and leaving behind tiny imperfections called vacancies. Far from being flaws, these vacancies can behave as qubits — the fundamental building blocks of quantum information.
The challenge is precision.
Researchers want to place these quantum defects exactly where they need them, but until now they have had only a limited understanding of what happens inside a crystal during the instant when a laser creates the defect.
“Our long-term goal is deterministic defect creation. We want to be able to place a quantum defect exactly where we intend it to go every time.” — Haidan Wen, Argonne scientist
Scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory have now taken an important step toward solving that problem.
Using the Advanced Photon Source (APS), a DOE Office of Science user facility, the team developed a new X-ray imaging technique that lets them watch, in three dimensions and in real time, how silicon carbide responds immediately after an ultrafast laser pulse strikes it. Their work provides real-time pictures of how the laser’s energy moves through the material — a key step toward building quantum devices with atomic precision.
The research appears in ACS Nano and was supported by Q-NEXT, a DOE National Quantum Information Science Research Center led by Argonne.
“Before you can precisely engineer quantum defects, you have to understand exactly what the laser is doing inside the material,” said Argonne scientist Haidan Wen, an author of the paper. “This technique lets us watch that process unfold, especially how atoms move in ways that weren’t possible before.”
Building better quantum materials
Drawing on the special features of quantum physics, quantum information technologies are expected to give us new ways to share information. They could speed drug discovery, help protect financial transactions and deliver solutions to currently intractable problems using quantum computation. The foundation of these technologies is the qubit.
Silicon carbide has emerged as one of the most promising qubit materials. It’s capable of hosting atomic-scale defects whose quantum states can store and process information. And it is already widely used by the semiconductor industry, making it an attractive platform for manufacturing future quantum technologies at scale.
Scientists create the defects by striking the crystal with ultrafast laser pulses lasting only millionths of a billionth of a second.
Compared with earlier methods that relied on electron or ion beams, lasers offer the possibility of creating vacancies at carefully chosen locations inside the crystal. But researchers have not fully understood exactly how the energy travels through the material before a vacancy forms.
“Our long-term goal is deterministic defect creation,” Wen said. “We want to be able to place a quantum defect exactly where we intend it to go every time.”
Using X-rays as a camera
To better understand the process, the researchers turned to the APS, one of the world’s brightest X-ray sources.
Their approach combines an ultrafast laser with an exceptionally small, highly focused X-ray beam. The laser initiates the process, while precisely synchronized X-ray pulses act like a camera, recording how the crystal responds over time.
Unlike visible light, hard X-rays penetrate deep into the material while remaining sensitive to the positions of individual atoms. That allowed the researchers to observe structural changes occurring beneath the surface — something conventional optical techniques cannot easily accomplish. Researchers used Argonne’s Center for Nanoscale Materials — another DOE Office of Science user facility — to interpret the X-ray diffraction patterns, using them to measure how the silicon carbide changed.
The team also achieved exceptionally fine spatial resolution by focusing the X-ray beam to hundreds of nanometers across — a hundred times thinner than the width of a human hair.
“This gives us a way to see not only what’s happening on the surface, but also how the response evolves deep inside the crystal,” said Argonne scientist Stephan Hruszkewycz, one of the paper’s authors. “That depth information has been missing, and it’s essential for understanding how laser-written quantum defects form.”
Following energy through the crystal
The measurements revealed two distinct ways that energy travels after the laser pulse.
Part of the energy moves rapidly through the crystal as an organized mechanical wave, similar to ripples spreading across a stretched surface after it is struck. At the same time, some of the energy slowly disperses as heat, causing nearby atoms to vibrate randomly before the crystal gradually returns to equilibrium.
For the first time, the researchers were able to directly image how these different energy-transport processes evolve both across the surface and into the depth of the material. Being able to image energy’s propagation from the crystal’s surface to the interior introduces a level of detail previously out of reach.
To visualize the process, imagine dropping a bowling ball onto a hefty rubber slab. The impact sends a ripple through the material. The laser creates a similar disturbance inside the crystal, and the APS serves as an ultrafast camera, capturing a sequence of X-ray images that reveal how the disturbance spreads and fades billionths of a second after the laser strikes.
Understanding this behavior could eventually help scientists fine-tune laser-writing conditions to produce more reliable quantum defects.
“Every improvement in our understanding brings us closer to engineering quantum materials instead of discovering them by trial and error,” Hruszkewycz said.
A platform for future discoveries
Although the study focused on silicon carbide, the researchers say the imaging approach can be adapted to many other materials used in quantum information science.
The work also highlights the unique capabilities available at the APS, where advanced X-ray optics, ultrafast laser systems and precise timing electronics make experiments like this possible.
For Argonne, which combines expertise in quantum information science with world-class materials characterization, the project demonstrates how new measurement tools can accelerate the development of future quantum technologies.
The ability to watch materials respond in real time does not itself create better qubits. But by revealing the physical processes that govern their formation, it gives scientists the knowledge needed to improve how they manufacture them.
“Our goal isn’t just to observe these processes,” Wen said. “It’s to learn enough from them that we can eventually build quantum devices with the level of precision that practical quantum technologies will require.”
Co-authors with Hruszkewycz and Wen are Kumar Neeraj, Matthew J. Highland, Tao Zhou, Burak Guzelturk, Donald A. Walko, Nathan C. Flanders, Nazar Delegan, F. Joseph Heremans and Martin V. Holt.
This material is based upon work supported by the DOE’s Office of Science National Quantum Information Science Research Centers as part of the Q-NEXT center.
About Argonne’s Center For Nanoscale Materials
The Center for Nanoscale Materials is one of the five DOE Nanoscale Science Research Centers, premier national user facilities for interdisciplinary research at the nanoscale supported by the DOE Office of Science. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge, Sandia and Los Alamos National Laboratories. For more information about the DOE NSRCs, please visit https://science.osti.gov/User-Facilities/User-Facilities-at-a-Glance.
About The Advanced Photon Source
The U. S. Department of Energy Office of Science’s Advanced Photon Source (APS) at Argonne National Laboratory is one of the world’s most productive X-ray light source facilities. The APS provides high-brightness X-ray beams to a diverse community of researchers in materials science, chemistry, condensed matter physics, the life and environmental sciences, and applied research. These X-rays are ideally suited for explorations of materials and biological structures; elemental distribution; chemical, magnetic, electronic states; and a wide range of technologically important engineering systems from batteries to fuel injector sprays, all of which are the foundations of our nation’s economic, technological, and physical well-being. Each year, more than 5,000 researchers use the APS to produce over 2,000 publications detailing impactful discoveries, and solve more vital biological protein structures than users of any other X-ray light source research facility. APS scientists and engineers innovate technology that is at the heart of advancing accelerator and light-source operations. This includes the insertion devices that produce extreme-brightness X-rays prized by researchers, lenses that focus the X-rays down to a few nanometers, instrumentation that maximizes the way the X-rays interact with samples being studied, and software that gathers and manages the massive quantity of data resulting from discovery research at the APS.
This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
About Q-NEXT
Q-NEXT is a U.S. Department of Energy National Quantum Information Science Research Center led by Argonne National Laboratory. The center brings together world-class researchers from national laboratories, universities and technology companies with the goal of developing the science and technology to control and distribute quantum information. Q-NEXT develops networks of sensors and secure communications systems, creates materials for scalable quantum devices, and trains the next-generation quantum-ready workforce to ensure continued U.S. scientific and economic leadership in the rapidly advancing field of quantum information science. For more information, visit https://q-next.org/.
About Argonne National Laboratory
Argonne National Laboratory seeks solutions to pressing national problems in science and technology by conducting leading-edge basic and applied research in virtually every scientific discipline. Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science.
About The U.S. Department of Energy’s Office
The U.S. Department of Energy’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit https://energy.gov/science.
Source: Argonne National Laboratory