Building Better Qubits

While growing up in Germany, Heike Riel helped her father design and build furniture in the family workshop. She says the experience taught her that “precision and creativity are necessary to build something excellent.”

“Working as a furniture maker was actually a very nice experience because you built something that is high quality and lasts,” Riel says. “When I go back to my hometown, many of our clients still have the furniture that I helped build for them.”

Woodworking also instilled in her a passion for mathematics and physics, she says, adding that she knew she someday would pursue a career in one of those fields.

Today the IEEE senior member is head of science and technology at IBM Research in Zurich. She is also the lead for IBM Research Quantum Europe and Africa, a group that aims to create technologies in artificial intelligence, nanotechnology, quantum computing, and related fields.

The IBM Fellow has helped develop several groundbreaking technologies including OLED displays. She has conducted research in semiconducting nanowires and other nanostructures, as well as molecular electronics. She has authored more than 150 publications and holds more than 60 patents.

Riel is the recipient of this year’s IEEE Andrew S. Grove Award “for contributions to materials for nanoscale electronics and organic light-emitting devices.” The award is sponsored by the IEEE Electron Devices Society.

“I couldn't believe that I was selected [to receive] this very prestigious award,” Riel says. “I feel very humbled and honored because I have great respect for Andrew S. Grove, who was a true technical and business leader in the semiconductor industry, and many people I admire have received this award.”

THE FIRST OLED DISPLAY

After completing a woodworking apprenticeship in 1989, Riel decided to pursue a master’s degree in physics. She graduated in 1997 from Friedrich-Alexander-Universität Erlangen-Nürnberg, in Germany. She joined IBM Research in Zurich in 1998 while pursuing her doctorate in physics in collaboration with the University of Bayreuth, also in Germany.

Her research focused on the optimization of multilayer organic light-emitting devices to be used in displays. After earning her Ph.D. in 2003 she worked at the lab as a research staff member. Riel’s research helped explain the physics behind charge transport and recombination, which govern the operation of all electronic devices, as well as light outcoupling in organic semiconductors.

“Back then, people didn’t believe it could be done, but that didn’t stop us.”

Her findings helped improve the efficiency, color, and endurance of OLEDs, which made it possible for her and the team to develop the first 51-centimeter full-color active-matrix OLED display. The technology is made by placing thin films of light-emitting organic compounds between two conductors. When voltage is applied, a bright light is emitted from each individual pixel. OLEDs can be found in TV screens, tablets, and smartphones.

“We had one year to scale organic LEDs to make a 20-inch display in three different colors with pixel sizes of 100 micrometers by 300 micrometers,” Riel said in a 2021 interview for IBM’s Research blog. “Back then [in the early 2000s], people didn’t believe it could be done, but that didn’t stop us.”

She says it’s rewarding to have developed something consumers use every day.

“When my husband bought our first OLED television, it was really exciting,” she recalls. “Suddenly I owned a product that is using technologies I developed.”

NANOWIRE TRANSISTORS

Riel went on to become head of IBM’s nanoscale electronics group, which develops semiconducting nanowires and nanostructures for transistors. She and her team helped develop the first vertical surround-gate nanowire field-effect transistor in 2006.

Researchers around the world had been trying to reduce the size of transistors for decades. But each time the transistors were miniaturized, their performance decreased; eventually they couldn’t effectively control electric current.

“It became clear,” Riel says, “that how we built transistors had to change in the early 2000s.”

“We had to come up with new ideas for how to improve the quality of [transistors] when we make them smaller,” she says. “We explored and developed new materials and integration schemes for nanoscale electronics and new transistor architectures based on semiconducting nanowires.”

Riel and her team implemented gate-all-around and cylindrical nanowires for transistors. Because the nanowires are cylindrical, the transistor gate can be wrapped around the nanowires—which allows better control of the current, according to a research paper authored by Riel and her colleagues.

In 2017 IBM released a new transistor—the Nanosheet—that uses the concepts Riel says she and her team developed between 2005 and 2012. Each transistor is made up of three stacked horizontal silicon sheets, each a few nanometers thick and completely surrounded by a gate. Last year IBM unveiled the world’s first 2-nm node chip, which was based on Nanosheet technology.

“IBM claims this new chip will improve performance by 45 percent using the same amount of power, or use 75 percent less energy while maintaining the same performance level, as today’s 7 nm-based chips,” anIEEE Spectrum article said.

ENHANCING THE QUBIT

Riel is currently conducting quantum-computing research. She and her team are developing qubits and related technologies.

Classical computers switch transistors on and off to represent data as ones or zeros. Because of the nature of quantum physics, qubits can be in a state of superposition, whereby they are both 1 and 0 simultaneously, as explained in a 2020 IEEE Spectrum article. Quantum computers can perform some tasks far faster and more accurately than conventional machines.

“We are trying to figure out whether a new material would make them function better and if [certain materials] could have advantages over today’s processors,” Riel says. Her team has been experimenting with silicon spin qubits and topological phenomena.

She and her team are taking a holistic approach, she says, and are building a quantum system from the ground up—creating the qubit, quantum processor unit technology, control electronics, and software. In November the IBM team demonstrated the Eagle, a 127-qubit chip: the world’s first quantum processor to break the 100-qubit barrier.

Her team also is working to find a good way to connect two quantum processors. In quantum computing, she says, transduction is necessary to transport information over a long distance from one processor to another. Quantum transduction is the process of converting quantum signals from a low-energy photon to a high-energy photon to protect its state during transmission.

“To do this conversion, you need sophisticated technology,” Riel says. “We are exploring different approaches and figuring out which is the best and how we can achieve the specifications that you need for doing it.”

CONNECTING THROUGH IEEE

Riel says she joined IEEE in 2007 so she could contribute to the community, participate in conferences, and connect with other engineers.

A member of the IEEE Electron Devices Society, she has helped to organize events including the IEEE European Solid-State Device Research Conference, the IEEE International Electron Devices Meeting, and the IEEE Symposium on VLSI Technology and Circuits.

Riel says IEEE has enriched her career, allowing her to keep up with technology advances and to network with peers.