Quantum Control Breakthrough a Game Changer for Next-Gen Electronics and Computers

Breakthrough in Quantum Control: A Game-Changer for Next-Gen Electronics and Computers

Researchers from Penn State have unveiled a groundbreaking method to manipulate the flow of electrons in quantum materials, opening up new possibilities for advanced electronics and quantum computing.

In a significant milestone, scientists have successfully demonstrated the electronic manipulation of electron flow direction in promising quantum computing materials for the first time. This achievement comes in the form of a novel electrical method that could revolutionize the development of next-generation electronic devices and quantum computers. The research team, hailing from Penn State, conducted their experiments on materials exhibiting the quantum anomalous Hall (QAH) effect—a phenomenon where electrons flowing along the edge of a material do not dissipate energy. The results of their work were published on October 19 in the journal Nature Materials.

The Significance of Electron Flow Control

In an era where electronic devices are shrinking while computational demands are increasing, optimizing the efficiency of information transfer, including electron flow control, is of paramount importance. According to Cui-Zu Chang, Henry W. Knerr Early Career Professor and associate professor of physics at Penn State, and co-corresponding author of the paper, “The QAH effect is promising because there is no energy loss as electrons flow along the edges of materials.”

The Quantum Anomalous Hall (QAH) effect was initially experimentally demonstrated by Chang in 2013. Materials that exhibit this effect, known as QAH insulators, are a subset of topological insulators—extremely thin films, only a few dozen atoms thick—made magnetic to conduct current solely along their edges. This one-directional electron flow is described as dissipationless, as it incurs no energy loss in the form of heat.

A Novel Electrical Method for Electron Control

“In a QAH insulator, electrons on one side of the material travel in one direction, while those on the other side travel in the opposite direction, like a two-lane highway,” Chang explained. “Our earlier work demonstrated how to scale up the QAH effect, essentially creating a multilane highway for faster electron transport. In this study, we develop a new electrical method to control the transport direction of the electron highway and provide a way for those electrons to make an immediate U-turn.”

To achieve this, the researchers crafted a QAH insulator with specific, optimized properties. They found that applying a 5-millisecond current pulse to the QAH insulator impacted the material’s internal magnetism, causing the electrons to change directions. This ability to change the flow of electrons is crucial for optimizing information transfer, storage, and retrieval in quantum technologies. Unlike conventional electronics, where data is stored as binary states (either one or zero), quantum data can exist in a range of possible states simultaneously. Altering the direction of electron flow is a pivotal step in writing and reading these quantum states.

Shifting from Magnetic to Electronic Control

Chao-Xing Liu, professor of physics at Penn State and co-corresponding author of the paper, emphasized the importance of the shift from magnetic to electronic control in quantum materials. He stated, “The previous method to switch the direction of electron flow relied on an external magnet to alter the material’s magnetism, but using magnets in electronic devices is not ideal. Bulky magnets are not practical for small devices like smartphones, and an electronic switch is typically much faster than a magnetic switch. In this work, we found a convenient electronic method to change the direction of electron flow.”

The researchers had previously optimized the QAH insulator to exploit a physical mechanism within the system that controlled its internal magnetism. Liu added, “To make this method effective, we needed to increase the density of the applied current. By narrowing the QAH insulator devices, the current pulse resulted in very high current density that switched the magnetization direction, as well as the direction of the electron transport route.”

A Parallel with Traditional Memory Storage

The transition from magnetic to electronic control in quantum materials mirrors a shift that occurred in traditional memory storage. In the past, data storage on hard drives and floppy disks involved magnets to create a magnetic field for writing data. In contrast, modern “flash memory” used in USB drives, solid-state hard drives, and smartphones relies on electronic writing. Emerging memory technologies, like MRAM, also leverage physical mechanisms related to internal magnetism.

Theoretical Insights and Future Endeavors

Beyond their experimental breakthrough, the research team provided a theoretical interpretation of their methodology. Currently, they are exploring ways to interrupt electrons on their path, effectively switching the system on and off. Additionally, they are researching how to demonstrate the QAH effect at higher temperatures.

Chang expressed the long-term goal, saying, “This effect, as well as current requirements for quantum computers and superconductors, require very low temperatures near absolute zero. Our long-term goal is to replicate the QAH effect at more technologically relevant temperatures.”

This research was funded by the Army Research Office, the Air Force Office of Scientific Research, and the National Science Foundation (NSF). Additional support was provided by the NSF-funded Materials Research Science and Engineering Center for Nanoscale Science at Penn State and the Gordon and Betty Moore Foundation’s EPiQS Initiative.

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• Read the full research paper in Nature Materials