Resolution of Qubit Decoherence: Coherence Collapse as a Deterministic Phase Transition in Coupled Oscillator Networks

We propose that qubit decoherence in superconducting quantum computers is not random noise but a deterministic phase transition in a coupled oscillator network. Each qubit is modeled as a phase oscillator with natural frequency omega_i, coupled with strength K to its neighbors. Coherence is quantified by the Kuramoto order parameter r = |mean(exp(2 pi i theta))|. A critical coupling K_c = 2 sigma_omega / pi separates two regimes: below K_c, phases desynchronize and coherence collapses (r approaches 0, T2 ~ 100 microseconds); above K_c, phases lock and coherence is maintained (r approaches 1, T2 can exceed milliseconds). Current superconducting qubits operate at K/K_c ~ 0.5, deep in the decoherent regime. We show that phase-optimized coupling at K/K_c = 5 on the same hardware could increase T2 by an order of magnitude, potentially transforming quantum error correction overhead.