Spectral Noise Engineering: A Platform-Agnostic Co-Design Framework for Room-Temperature Quantum Coherence Extension

We introduce Spectral Noise Engineering (SNE), a platform-agnostic framework for extending spin coherence times T₂ at room temperature through the co-design of material encapsulation layers and dynamic decoupling sequences. The framework is built on the Guaranteed Spectral Orthogonality (GSO) metric Λ, which quantifies the spectral overlap between the suppression transfer functions of any two candidate protection mechanisms. We demonstrate computationally that ln(G_combined/G_max) scales linearly with ln(Λ) (R² = 0.991) across all tested mechanism combinations for NV centers in nanodiamonds and MOF molecular qubits, validating that Λ quantitatively governs super-additive coherence gains. For the NV platform calibrated on Zvi et al. (PNAS 2025), the full SNE stack (SiO₂ passivation + CPMG-64) achieves T₂ = 2.38 ms with Λ(SiO₂, CPMG-64) = 0.019 and a manufacturing-robust median of 0.12 ms (Monte Carlo P10-P90: 0.07-0.21 ms). For MOF molecular qubits calibrated on RSC Chem. Commun. (2024), adding CPMG-64 to the existing PDI-nitroxide/UiO-MOF deuterated baseline of 0.70 ms yields a simulated median T₂ = 1.19 ms (56% of realizations exceed 1 ms). For hBN VB⁻ defects with ¹⁰B isotopic enrichment plus CPMG-16, Monte Carlo gives median T₂ = 14.57 µs (×7.3, 71.5% > 10 µs gate). The framework also introduces Active Spectral Shifting — a design equation r_min = √(2DT/πN) that engineers material geometry to align translational diffusion noise with the optimal CPMG passband, constituting a falsifiable experimental prediction for ND diameters ≥ 212 nm. These results establish SNE as a quantitative, machine-executable methodology for room-temperature quantum coherence engineering, laying the algorithmic foundation for automated Quantum EDA platforms.