Noise or Signal? A Causal Mediation Analysis of Quantum Circuit Learning Under Real Hardware Noise
Year: 2026
Type: conference-paper
Abstract: We deploy a Quantum Counterfactual Mediation Analysis (QCMA) framework on IBM Quantum processors to ask a precise, hardware-grounded question: are causal regimes identified in noiseless simulation preserved under real quantum noise? Integrating partial quantum state tomography with a linear structural equation model, we decompose inter-architectural performance contrasts into direct effects and indirect quantum-mediated effects across twelve experiments spanning three circuit topologies and two benchmark datasets. Five of six topology-dataset pairs (83%) retain their causal regime when migrating from noiseless simulation to physical hardware. Decoherence inflates quantum-mediated contributions by up to one order of magnitude a noise artefact, not quantum advantage while the Neutral regime dominates both backend. These findings indicate that hardware noise may substantially limit the effective utilization of quantum resources in current NISQ circuits, and motivate further investigation into coherence-preserving circuit design strategies.
Institution: Universidad de Deusto
Language: English
Subfield: Artificial Intelligence
Field: Computer Science
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W7204488049