Quantum kernel anomaly detection: a fidelity-based framework for robust behavioral biometric authentication
摘要
Behavioral biometric signals such as keystroke dynamics and gait are inherently non-stationary due to human adaptation, defined here as intra-user temporal drift across sessions arising from fatigue, cognitive load, device handling, and contextual variation. Because impostor data are typically unavailable at enrollment and genuine behavior evolves over time, biometric authentication is naturally formulated as a one-class anomaly detection problem rather than a fixed-distribution classification task. This work addresses the resulting generalization and stability challenges by representing behavioral consistency using fidelity-based similarity, inspired by quantum state overlap, where gradual fidelity decay provides a bounded and calibrated indicator of anomalous deviation. In the proposed quantum kernel-based anomaly detection (QKAD) framework, biometric feature sequences are mapped to quantum states via hybrid angle–amplitude encoding, behavioral similarity is evaluated using quantum kernel fidelity, and anomaly scores are produced by a classical one-class support vector machine (OC-SVM) operating on the induced kernel geometry. The framework is primarily evaluated using a noise-aware quantum simulator (