We tried to find quantum advantage. Here are the six things we got wrong: A feasibility study of output-aware tensor-network contraction against real quantum hardware

A feasibility study testing whether quantum circuits can be constructedwhere exact classical simulation cost grows much faster than the physicalcircuit depth needed to run them, using output-aware tensor-networkcontraction validated against two real IBM Quantum hardware jobs(dadm3mjdd5gc73d7gvjg, dadm9qdnj4cs73ae2teg; 40,960 shots total). The honest conclusion is no — not on any hardware available today. Reachingthat conclusion required correcting the study's own conclusions six times;those corrections, and the measurements behind them, are the primarycontribution. Key measured results: classical contraction cost scales as 2^w withmeasured exponent 1.984; effective two-qubit error on IBM's Heronarchitecture is gate-local at 0.845%, reproducible across two independentjobs; memory is not a binding constraint once slicing is applied (1.00-3.18xFLOP penalty); connectivity degree, not planarity, is the dominanttopological lever; standard error suppression (dynamical decoupling +twirling) made fidelity worse on this circuit class; qubit count sets a hardceiling on achievable classical hardness (2^n). This is a feasibility study, not an advantage claim: no quantum advantage,no novel algorithm (frontier contraction is textbook variable elimination),and no verified large-width result are claimed. Full reproducibility scriptsincluded.