Entanglement-Coupling Precursors of Decoherence in Quantum Circuits: A Heuristic Information-Theoretic Precursor Framework (KA-Quantum)

Decoherence is the primary obstacle to reliable quantum computing, yet real-time, measurement-driven early warning remains unavailable. Standard metrics (fidelity, entanglement entropy) are computed post-hoc or require full state tomography. We propose KA-Quantum, a thermodynamic early warning framework grounded in the Karimov–Alekberli (KA) causal entropy formalism [1], monitoring three quantum channels: C1 (von Neumann entropy deviation), C2 (bipartite correlation entropy coupling decay), and C3 (fidelity residual). Using Qiskit Aer density-matrix simulation [2] of N=5 qubit circuits across three circuit classes (GHZ, random, variational) and three noise models (amplitude damping, phase damping, depolarizing; 30 Monte Carlo runs each, linearly increasing noise ramp), we find: 5 of 9 configurations achieve DR = 100% (30/30); overall DR = 56% (150/270) including physically non-decaying regimes where the specific noise type does not drive fidelity below the 0.9 threshold within the simulation window. FPR = 0.00 in all calibration periods. Median lead times of 1–15 gate cycles (F < 0.9); lead time is invariant to KA threshold θ (2.0/2.5/3.0 tested), confirming empirical threshold invariance [3]. The C2 entanglement channel provides the earliest indicator, consistent with the structural coupling precursor that distinguishes KA across prior KA classical applications [4].