あらゆる材料に適用可能な量子ビット評価手法を確立～2次元材料・ヘテロ構造まで網羅～

2025-11-28 東北大学

図1. 位相緩和時間（T₂）の計算研究の発展史
1925～26年に量子力学の基礎方程式（シュレディンガー方程式・ハイゼンベルグ方程式）が確立した。1972年にT₂計算の理論原理が提案されたものの、実在材料では膨大な行列計算のため実用的な解析は困難だったが、2008年にクラスター相関展開法（CCE）により実用的な近似計算が可能となった。2021年に東北大学・シカゴ大学の共同研究により、三次元材料のT₂を代数的に表現できる「一般化スケーリング則」が発見された。本研究はこの理論を二次元およびヘテロ構造材料へと拡張するものである。

＜関連情報＞

• https://www.tohoku.ac.jp/japanese/2025/11/press20251128-01-bit.html
• https://www.tohoku.ac.jp/japanese/newimg/pressimg/tohokuuniv-press20251128_01web_bit.pdf
• https://www.nature.com/articles/s41699-025-00623-8

長いスピン量子ビットコヒーレンス時間を持つ2次元物質の探索戦略 Strategies to search for two-dimensional materials with long spin qubit coherence time

Michael Y. Toriyama,Jiawei Zhan,Shun Kanai & Giulia Galli
npj 2D Materials and Applications  Published:26 November 2025
DOI:https://doi.org/10.1038/s41699-025-00623-8

We are providing an unedited version of this manuscript to give early access to its findings. Before final publication, the manuscript will undergo further editing. Please note there may be errors present which affect the content, and all legal disclaimers apply.

Abstract

Two-dimensional (2D) materials that can host qubits with long spin coherence time (T₂) have the distinct advantage of integrating easily with existing microelectronic and photonic platforms, making them attractive for designing novel quantum devices with enhanced performance. However, the relative lack of 2D materials as spin qubit hosts, as well as appropriate substrates that can help maintain long T₂, necessitates a strategy to search for candidates with robust spin coherence. Here, we develop a high-throughput computational workflow to predict the nuclear spin bath-driven qubit decoherence and T₂ in 2D materials and heterostructures. We initially screen 1172 2D materials and find 189 monolayers with T₂ > 1 ms, higher than that of naturally-abundant diamond. We then construct 1554 lattice-commensurate heterostructures between high-T₂ 2D materials and select 3D substrates, and we find that T₂ is generally lower in a heterostructure than in the bare 2D host material; however, low-noise substrates (such as CeO₂ and CaO) can help maintain high T₂. To further accelerate the material screening effort, we derive analytical models that enable rapid predictions of T₂ for 2D materials and heterostructures. The models offer a simple, yet quantitative, way to determine the relative contributions to decoherence from the nuclear spin baths of the 2D host and substrate in a heterostructural system. By developing a high-throughput workflow and analytical models, we expand the genome of 2D materials and their spin coherence times for the development of spin qubit platforms.