A Unified periodic table of quantum coherence for isotope engineering

金井 駿*; 鈴木 誠也   ; Anderson, C. P.*

Kanai, Shun*; Suzuki, Seiya; Anderson, C. P.*

Quantum coherence underpins the performance of all quantum technologies, from error-resistant operations to long-lived quantum memories and ultrasensitive sensors. Despite steady advances, coherence remains fundamentally constrained by environmental noise, most notably, from nuclear spins embedded in the host lattice. Protocol-level strategies, such as dynamical decoupling or operation at clock transitions, mitigate this noise externally but impose control overhead. In contrast, materials-based approaches-especially isotopic purification-directly suppress decoherence at its source. Here, we introduce a unified periodic table of quantum coherence that quantifies coherence limits element by element, incorporating both natural isotope distributions and practical routes for isotopic enrichment. Importantly, this framework provides, for the first time, theoretical upper bounds (T2,max) for all stable elements, offering a quantitative ceiling on what isotopic purification can achieve. The table reveals where purification yields decisive improvements, where alternative strategies must prevail, and where supply or regulatory barriers constrain feasibility. Beyond guiding the search for solid-state qubit hosts, it uncovers overlooked opportunities in functional oxides and related compounds. More broadly, this framework positions isotope engineering as an increasingly important tool for identifying and realizing future quantum-coherent materials.