Software‑Defined Vehicular Networks (SDVN) are the backbone of smart mobility, yet their centralized design makes them easy targets. A Distributed Denial of Service (DDoS) attack can flood the central controller, cutting off communication between cars and infrastructure. To fight this, researchers built a hybrid model that blends classical AI with quantum computing. At its core lies a Classical‑Quantum Neural Network (C‑QNN), which merges PennyLane quantum circuits with a traditional neural net. Two other variants were tested: a Classical‑Quantum Boltzmann Machine (C‑QBM) and a Classical‑Quantum K‑Means (C‑QKM). Experiments ran on a simulated vehicular network with cars moving between 0 and 100 km/h, using two DDoS datasets (UNB‑CIC‑DDoS and Kaggle DDoS). The C‑QNN outperformed the rest, achieving 99 % accuracy on the first dataset and 90 % on the second. These results show that quantum circuits can boost the ability to separate legitimate from malicious traffic, paving the way for stronger defenses in future connected cities.
The proposed hybrid model leverages quantum circuits' ability to represent superposition and entanglement, boosting feature space dimensionality without adding classical parameters. Practically, each traffic datum (e.g., packet count, connection duration, average payload size) is encoded into an input vector feeding a traditional neural network. Simultaneously, the same vector undergoes a series of parametrized qubit rotations (RX, RY, RZ) implemented in PennyLane. The resulting quantum state’s probability amplitudes embed non‑linear information hard to capture with purely classical methods. During training, the algorithm optimizes both the classical network weights and the quantum gate parameters, minimizing a cross‑entropy loss. The Classical‑Quantum Boltzmann Machine (C‑QBM) uses a quantum Boltzmann distribution where state probabilities follow a quantum Gibbs formalism, but it is more sensitive to simulator noise. The Classical‑Quantum K‑Means (C‑QKM) applies quantum clustering, exploiting the Bures distance between density matrices to group traffic flows. Datasets include UNB‑CIC‑DDoS (10 million labeled flows) and Kaggle DDoS (more diverse but less balanced). Evaluation metrics (accuracy, precision, recall, F1‑score) reveal that C‑QNN maintains an optimal trade‑off between generalization and computational complexity, aided by quantum regularization techniques such as entanglement entropy penalization. This approach shows how integrating quantum modules can enhance real‑time defense systems, paving the way for future deployment on actual quantum hardware where execution latency will be further reduced.
