Boundary-Geometry Stabilization of Superconducting Qubits Under Rapid Relaxation Fluctuations

Superconducting qubit relaxation rates are known to fluctuate on millisecond timescales due to time-varying system–environment couplings. Standard characterisation methods average over these fluctuations, obscuring regime transitions in effective coherence. This work introduces a task-calibrated boundary-geometry formulation of qubit stability in which the time-dependent decoherence-per-gate ratio ρ(t) defines a stability margin relative to a declared performance threshold ρ*. A threshold-conditional scheduling policy is derived that parks computation when the stability margin becomes negative. Ensemble stochastic telegraph simulations (N = 200 accepted realisations) demonstrate 78.7% per-gate error reduction at equal useful-gate count and 19.7% active-time reduction, in agreement with analytical prediction (79.2%). Estimator-delay sensitivity is quantified via a dimensionless parameter τ̂ = τ_est · k↓, yielding a falsifiable requirement τ̂ ≲ 0.2 for sustained benefit. The framework does not claim microscopic mechanism closure. It provides a governance-constrained, falsifiable control architecture for stabilising coherence under rapid relaxation fluctuations and defines explicit promotion/demotion conditions under TRIDENT/USDOP v1.2. External comparator: Rational Quantum Mechanics (Palmer, PNAS 2026, doi:10.1073/pnas.2523350123) independently proposes discrete admissibility constraints as the mechanism by which certain quantum states become structurally inaccessible. Structural similarity with the boundary-geometry and admissibility-gating logic of this framework is noted; equivalence is neither asserted nor implied. Keywords Superconducting qubits Qubit relaxation fluctuations Real-time adaptive estimation Decoherence mitigation Threshold-conditional scheduling Coherence stabilisation Boundary-state formalism Stability margin Telegraph noise model Stochastic control Estimator latency Quantum hardware control architecture TRIDENT governance USDOP v1.2 SHRF framework Related corpus works • TRIDENT-Z0 Diagnostic Framework: USDOP v1.2https://doi.org/10.5281/zenodo.18721255 • Optimization as Fragility: Boundary Over-Control and Coherence Collapsehttps://doi.org/10.5281/zenodo.18686580