Sustainability Cost of Defect Engineering in Color Centers for Quantum Communications

Quantum communication relies on hardware that distributes entanglement over long distances with stability and scalability. Color centers in diamond, silicon carbide (SiC), hexagonal boron nitride (h-BN), gallium nitride (GaN), and zinc oxide (ZnO) are leading solid-state qubit platforms. Yet, their fabrication through ion implantation, electron beam irradiation, laser writing, and heteroepitaxial growth imposes substantial but unexamined sustainability costs. In this study, we construct inventories to evaluate twenty paired combinations of substrate and defect engineering techniques using a cradle-to-gate, multi-attribute framework that integrates life cycle assessment (LCA), chemical hazard assessment (CHA), and human health toxicity (HHT). Cumulative energy demand (CED), global warming potential (GWP), water use, and toxicological burden are quantified. Results show femtosecond laser writing in h-BN exhibits the lowest impacts across all metrics, with CED of < 0.1 GJ/chip, GWP < 20 kg CO2 eq., and near-zero CHA and HHT scores, 1–2 orders of magnitude lower than ion-implantation in diamond or SiC. Despite high performance, diamond and SiC impose ecological and human health burdens due to thermally intensive growth and hazardous post-defect stabilization chemistries. Laser writing in h-BN, ZnO, and GaN shows greener-by-design pathways, providing a roadmap for reducing environmental trade-offs in host crystals and advancing climate-aligned quantum communication infrastructure.