SLT-2 Phenomenological Model of Residual Decoherence in Superconducting Qubits

This work develops a phenomenological model of residual decoherence in superconducting transmon qubits within the framework of State Locality Theory (SLT‑2). The model treats a qubit as a stable localized field configuration and introduces a frequency‑dependent localization rate that increases at lower transition energies. Using phenomenologically calibrated parameters, the model predicts a fundamental coherence‑time ceiling in the millisecond range and yields a falsifiable experimental signature: after subtracting all known noise mechanisms, the remaining decoherence rate should scale linearly with the inverse qubit frequency. Comparison with recent state‑of‑the‑art devices suggests that the SLT‑2 contribution may already constitute a significant fraction of the residual decoherence budget in low‑frequency qubits. The work also outlines an experimentally accessible protocol for testing this prediction using tunable‑frequency transmons. Additional SLT‑2 materials, extensions, and working notes are available in the associated OSF project: 10.17605/OSF.IO/CMVJ5.