Tiny Titans of Tech: How Moiré Excitons Are Advancing Quantum Computing

An artist’s rendering of moiré excitons in a nano-semiconductor. Credit: KyotoU/Matsuda Lab

Researchers at Kyoto University have developed a groundbreaking method to measure the quantum coherence time of moiré excitons, potentially improving qubits for <span class="glossaryLink" aria-describedby="tt" data-cmtooltip="

quantum computing

Performing computation using quantum-mechanical phenomena such as superposition and entanglement.

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By using advanced microfabrication and etching techniques combined with Michelson interferometry, they observed enhanced stability in quantum coherence at extremely low temperatures, significantly outperforming traditional excitons in <span class="glossaryLink" aria-describedby="tt" data-cmtooltip="

semiconductors

Semiconductors are materials with electrical conductivity that falls between conductors and insulators, making them essential for modern electronics. They are typically crystalline solids, the most common of which is silicon, used extensively in the production of electronic components such as transistors and diodes. Semiconductors are unique because their conductivity can be altered and controlled through doping—adding impurities to the material to change its electrical properties. This property allows them to serve as the foundation for integrated circuits and microchips, powering everything from computers and smartphones to advanced medical devices and renewable energy technologies. The behavior of semiconductors is also crucial in the development of various electronic, photonic, and quantum devices.

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Quantum technology is quantifiable in qubits, which are the most basic unit of data in quantum computers. The operation of qubits is affected by the quantum coherence time required to maintain a quantum wave state.

Scientists have hypothesized that moiré excitons — electron-hole pairs confined in moiré interference fringes that overlap with slightly offset patterns — may function as qubits in next-generation nano-semiconductors.

However, due to diffraction limits, it has not been possible to focus light enough in measurements, causing optical interference from many moiré excitons.

Breakthrough in Quantum Coherence Measurement

To solve this, Kyoto University researchers have developed a new method of reducing these moiré excitons to measure the quantum coherence time and realize quantum functionality. The team has observed changing photoluminescence signals of moiré excitons following the fabrication process.

“We combined electron beam microfabrication techniques with reactive ion etching. By utilizing Michelson interferometry on the emission signal from a single moiré exciton, we could directly measure its quantum coherence time,” Kazunari Matsuda of KyotoU’s Institute Advanced Energy explains.

Implications for Quantum Computing

The results show that the quantum coherence of a single moiré exciton remains steady at -269°C for more than 12 picoseconds, ten times longer than that of an exciton in the parent material, a two-dimensional semiconductor. The confined moiré excitons in interference fringes prevent loss of quantum coherence.

“We plan to establish a foothold for the next phase of experiments for advancing quantum computing and other quantum technologies in the next generation of nano-semiconductors,” adds Matsuda.

Reference: “Quantum coherence and interference of a single moiré exciton in nano-fabricated twisted monolayer semiconductor heterobilayers” by Haonan Wang, Heejun Kim, Duanfei Dong, Keisuke Shinokita, Kenji Watanabe, Takashi Taniguchi and Kazunari Matsuda, 8 June 2024, <span class="glossaryLink" aria-describedby="tt" data-cmtooltip="

Nature Communications

<em>Nature Communications</em> is an open-access, peer-reviewed journal that publishes high-quality research from all areas of the natural sciences, including physics, chemistry, Earth sciences, and biology. The journal is part of the Nature Publishing Group and was launched in 2010. "Nature Communications" aims to facilitate the rapid dissemination of important research findings and to foster multidisciplinary collaboration and communication among scientists.

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DOI: 10.1038/s41467-024-48623-4