Pinpointing The Glow Of A Single Atom
Argonne’s Quantum Emitter Electron Nanomaterial Microscope enables scientists to track and create quantum emitters for next-generation devices
Researchers have discovered how to design and place single-photon sources at the atomic scale inside ultrathin 2D materials, lighting the path for future quantum innovations.
Like perfectly controlled light switches, quantum emitters can turn on the flow of single particles of light, called photons, one at a time. These tiny switches — the “bits” of many quantum technologies — are created by atomic-scale defects in materials. Their ability to produce light with such precision makes them essential for the future of quantum technologies, including quantum computing, secure communication and ultraprecise sensing. But finding and controlling these atomic light switches has been a major scientific challenge — until now.
Scientists at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and the University of Illinois Urbana-Champaign have made a breakthrough in understanding and controlling quantum emitters. At the Center for Nanoscale Materials (CNM), a DOE Office of Science user facility at Argonne, the team used a state-of-the-art, specialized microscope called QuEEN-M (Quantum Emitter Electron Nanomaterial Microscope) to pinpoint and even create quantum emitters in an ultrathin material known as hexagonal boron nitride. By figuring out the atomic structure responsible for light emission, the researchers have opened the door to designing materials with custom quantum properties for future devices.
“The challenge in studying quantum emitters is that their optical behavior is determined by their atomic structure, which is very hard to observe directly,” said Jianguo Wen, an Argonne materials scientist.
Studying the light emission from quantum emitters usually requires thicker samples, while analyzing their atomic structure needs thinner samples. This tradeoff has made it difficult to fully understand these tiny light sources.
“The ability to place photons with high accuracy is crucial for tomorrow’s quantum devices.” - Benjamin Diroll, Argonne scientist
To solve this problem, Wen and his team used a technique called cathodoluminescence spectroscopy, along with the high-resolution QuEEN-M microscope. In cathodoluminescence, a focused beam of electrons excites the material, causing it to emit light. The color and intensity of the emitted light reveal information about what the quantum emitter is made of and its defect sites.
“The QuEEN-M is a specially designed electron microscope that takes advantage of modern electron optics and detectors,” added Jian-Min Zuo, Illinois Grainger Engineering professor of materials science and engineering. “Research infrastructure like this is essential for advancing future technology.”
The team discovered that twisting layers of hexagonal boron nitride at certain angles — a process that creates “twisted interfaces” — makes the light signal from quantum emitters much stronger, sometimes by up to 120 times. This stronger signal allowed the researchers to pinpoint the location of the emitters with incredible accuracy, down to less than 10 nanometers, or 10 billionths of a meter.
Using this powerful approach, the team identified the atomic structure of a blue quantum emitter in hexagonal boron nitride as a pair of vertically stacked carbon atoms, known as a carbon dimer. Even more impressively, the researchers showed that they could create these quantum emitters on demand by adding carbon to the material and using the electron beam to activate emitters at chosen spots.
“Once we could connect the atomic structure with the light it gives off, it opened the door to precise engineering of these quantum emitters,” Argonne scientist Thomas Gage explained. “We can now create and adjust them on demand using an electron beam.”
This ability to engineer quantum emitters with such precision marks a significant step forward for quantum technology.
“The ability to place these photons with high accuracy is crucial for tomorrow’s quantum devices,” noted Argonne scientist Benjamin Diroll.
This research makes it possible to build materials with custom quantum properties that can be placed exactly where needed on a chip. By doing this, scientists can connect these materials with other technologies to boost signals and share information more efficiently. This breakthrough will help speed up the creation of future quantum technologies.
Other contributors to this work include Muchuan Hua, Venkata Surya Chaitanya Kolluru, Wei-Ying Chen and Maria Chan from Argonne; Kaijun‑Yin and Pinak Tripathi from the University of Illinois Urbana-Champaign; and Hanyu Hou from both Argonne and the University of Illinois Urbana-Champaign.
Results of this research were published in Advanced Materials. This study was funded by the DOE Office of Basic Energy Sciences and the Laboratory Directed Research and Development program at Argonne. This research was also supported by QIS research funding. Additionally, this research used the Intermediate Voltage Electron Microscope, a partner facility of the Nuclear Science User Facilities supported by the DOE’s Office of Nuclear Energy.
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.
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.
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