A pathway to advanced quantum devices with zinc oxide quantum dots

A pathway to advanced quantum devices with zinc oxide quantum dots
by Riko Seibo
Tokyo, Japan (SPX) Nov 27, 2024

Researchers at Tohoku University have achieved a major advancement in quantum technology by creating electrically defined quantum dots within zinc oxide (ZnO) heterostructures. Their findings, published in Nature Communications on November 7, 2024, highlight zinc oxide's untapped potential for quantum computing applications.

Quantum dots are nanometer-scale semiconductor structures capable of trapping electrons, making them indispensable for quantum computing as they allow precise control over electron behavior. While materials like gallium arsenide (GaAs) and silicon have dominated quantum dot research, zinc oxide, known for its strong electron correlation and excellent spin quantum coherence, had remained largely unexplored for electrically defined quantum dots.

The research team successfully manipulated quantum dots in zinc oxide using fine voltage adjustments, akin to tuning a radio signal. This approach enabled them to observe the Coulomb diamond, a signature feature of quantum dots, shedding light on electron behavior within the material.

"The Coulomb diamond is like a fingerprint that helps identify the unique 'personality' of each quantum dot," explained Tomohiro Otsuka, associate professor at Tohoku University and the study's corresponding author. "By using zinc oxide, we're opening up new frontiers developing efficient and stable qubits, a cornerstone for quantum computing."

A standout discovery was the observation of the Kondo effect in zinc oxide quantum dots. This quantum phenomenon, wherein electron interactions lead to conduction, typically follows specific patterns based on the number of electrons in a dot. However, in zinc oxide, the Kondo effect manifested in unconventional ways, suggesting that the material's strong electron correlation introduces novel behaviors and possibilities for quantum device development.

"The Kondo effect we observed is different from what we typically see in other semiconductors like GaAs," Otsuka added. "This difference could help us better understand electron behavior in this new material and improve our ability to control and manipulate qubits."

Building on these insights, the team aims to translate their discoveries into functional quantum devices, paving the way for further innovations in the field.

Research Report:Parity-independent Kondo effect of correlated electrons in electrostatically defined ZnO quantum dots