Quantum Compositional NLP for Arabic: Grammar, Morphology, and Word Sense in Circuit Topology

We present the first application of pregroup grammar-based quantum compositional natural language processing (QNLP) to Arabic — a morphologically rich, free-word-order language whose structural complexity provides a uniquely demanding testbed for theories of meaning composition in quantum circuits. Our system converts Arabic sentences into quantum circuits whose topology mirrors grammatical structure: subjects, verbs, and objects become quantum gates, and the typed dependencies between them — the pregroup grammar — determine how those gates are wired together. We conduct three controlled experiments spanning word order, morphological tense, and verb sense disambiguation, comparing quantum circuit methods against classical baselines including AraVec (Arabic word embeddings) and AraBERT (a pre-trained Arabic transformer). The central finding is a clean causal ablation: quantum circuits encoding only grammar topology, with no parameterised components, achieve exactly 50% on a matched-pair word order task where classical bag-of-words models fail (12.8%); adding a single layer of parameterised entangling gates raises performance to 64.9% (95% CI 62.8, 66.3). This 15-percentage-point gain — with zero variance at the ablation baseline across all seeds and folds — is entirely attributable to parameterised entanglement, establishing a clean causal claim. We additionally introduce the first vocabulary-controlled Arabic word sense disambiguation dataset, using matched sentence pairs and shared lexical pools to isolate structural from lexical disambiguation signals, and characterise a SPSA label inversion phenomenon whose rate is measurably reduced by ancilla qubit encoding. Arabic's Semitic root-and-pattern morphology has a formal correspondence to quantum tensor products — identified independently in the computational linguistics literature — that no other language in the existing QNLP literature shares, positioning Arabic as a theoretically motivated and practically significant target for quantum compositional methods.