QCOS: Operational Intelligence and Governance Layer for Reproducible Quantum Research Infrastructure

Quantum research infrastructures across Europe have rapidly expanded access to quantum processing units (QPUs) through EuroHPC initiatives, cloud platforms, and national facilities. However, operational inefficiencies — including uncontrolled evaluation counts, hardware calibration drift, lack of reproducibility artifacts, vendor lock-in, and cost opacity — result in 60–80% waste of quantum execution budgets and significant delays in scientific output. This technical report introduces QCOS (Quantum Computing Operating System), an operational intelligence and governance layer that sits between researchers and quantum backends. QCOS provides adaptive convergence control, hardware abstraction across vendors, automated generation of cryptographically signed reproducibility evidence bundles, real-time drift monitoring, and per-experiment cost intelligence. Benchmark results on production quantum hardware demonstrate 73–94% reductions in quantum circuit evaluations, 67–85% cost savings, and a 93% reduction in audit preparation time, while maintaining or improving scientific accuracy. Use cases covering EuroHPC compliance, multi-vendor procurement, reproducibility crisis mitigation, and budget overrun prevention are presented, alongside integration models for HPC centers such as LUMI-Q. QCOS is positioned as the missing operational layer required to transition quantum computing from experimental access to governed, auditable, and production-grade research infrastructure.