QCIVET: A Quantum--Classical Pipeline Integrity Framework with Contract-Based Subtype Verification and Hash-Chained Audit Traces

2026-05-13

AI Summary

Existing integrity verification methods struggle to ensure both semantic and syntactic consistency in the quantum stages of hybrid quantum-classical computing pipelines. This work proposes the first contract-based integrity verification framework, modeling pipelines as sequences of stages annotated with explicit specifications. The approach integrates hash-chain audit trails with observable deviation testing grounded in Liskov–Wing behavioral subtyping to simultaneously verify syntactic correctness and semantic fidelity. A novel multi-Pauli contract mechanism is introduced to defend against Z-only-sneaky coverage attacks, with formal guarantees of soundness, conditional completeness, and compositionality established under the diamond norm. End-to-end validation is demonstrated on the IBM Quantum Heron r2 processor, supporting real-world applications such as VQE-based drug discovery, and the open-source engine achieves per-stage latency below 1 millisecond.

Abstract

Hybrid quantum--classical pipelines increasingly support applications such as drug discovery, fraud detection, and cloud quantum processing unit (QPU) auditing, yet existing integrity-verification methods remain largely classical and fail to capture quantum-stage behaviour. We propose QCIVET, a contract-based integrity-verification framework that models a hybrid pipeline as a sequence of stages with explicit specifications and audits it at both syntactic and semantic levels. Syntactic integrity is enforced through a hash-chained audit trail with optional external anchoring, while semantic integrity at quantum stages is verified using a calibrated observable-deviation test grounded in the behavioural-subtyping discipline of Liskov and Wing. We prove soundness under the diamond-norm distance between quantum channels, conditional completeness for informationally complete observable families, and compositionality under inheritance chains. We further identify a class of Z-only-sneaky overrides that evade weak single-Pauli contracts but are exposed by multi-Pauli contracts. The framework is evaluated under calibration-derived noise models from IBM Quantum Eagle r3 and Heron r2 processors, and the subtype-separation protocol is validated end-to-end on a real ibm_fez (Heron r2) processor. QCIVET is instantiated on three representative applications: variational quantum eigensolver (VQE) for drug discovery, quantum-assisted fraud detection, and customer-side auditing of cloud QPU services. The reference implementation, including a real-time verification engine with sub-millisecond per-stage commit latency, is released as open source.

Problem

• quantum-classical pipelines
• integrity verification
• quantum behavior
• semantic integrity
• hybrid computing

Innovation

• quantum-classical pipeline
• contract-based verification
• behavioural subtyping
• hash-chained audit
• observable-deviation test