Maintenance-Limited Coherence in Superconducting Qubits: Empirical Tests of a Thermodynamic Persistence Constraint

This preprint is the third paper in a series on thermodynamic persistence and macroscopic identity. A recently proposed thermodynamic persistence constraint and its empirical test in biological and classical systems suggest that macroscopic identities operating under irreversible dynamics remain admissible only so long as cumulative irreversible dissipation remains finite. The condition does not introduce new dynamical laws or predict lifetimes; it excludes only those histories in which maintaining a coarse-grained identity would require unbounded irreversible entropy production. In this work I examine whether state-of-the-art superconducting qubit platforms are empirically compatible with such a persistence accounting. Using only published device parameters and order-of-magnitude estimates for control and dissipation, I construct an operational diagnostic quantity from independently measurable observables: coherence time, irreversible power dissipation, and device scale. I evaluate this diagnostic in two representative contexts: (i) idle coherence limited by energy relaxation and dephasing, and (ii) driven operation under repeated gate application as characterized by randomized benchmarking and error-per-gate metrics, including logical-level operation in surface-code experiments. Across these regimes, the empirical behavior mirrors that observed in classical and biological systems: coherence time and logical error rates vary primarily through changes in effective dissipation and noise, while the normalized cumulative irreversible burden associated with loss of a qubit’s operational identity remains finite and modest under realistic operating conditions. No violations of the proposed thermodynamic admissibility condition are found within the parameter ranges examined. These results do not establish a thermodynamic bound on quantum coherence or gate fidelities. They do, however, support the empirical viability of treating qubit-level persistence as constrained by cumulative irreversible effects within standard thermodynamic bookkeeping, in continuity with classical and biological systems.