[5E1-GS-6d] Language media processing

10:15 AM - 10:30 AM JST(1:15 AM - 1:30 AM UTC)

[5E1-GS-6d-06] Analysis of Unitary Composition and Syntactic Expressivity in Hol-CCG from a Quantum-inspired Perspective

Kenji Higuchi¹, 〇Ryosuke Yamaki¹, Tadahiro Taniguchi^2,1 (1. Ritsumeikan University, 2. Kyoto University)

Keywords:

Quantum-inspired Language Model,Syntactic Parsing,Unitary Transformation,Combinatory Categorial Grammar

While Large Language Models (LLMs) demonstrate remarkable performance, their internal representations remain a black box, making it difficult to interpret how linguistic knowledge is processed. To address this challenge, Quantum-inspired Language Models have garnered attention for their high mathematical transparency. However, although these models capture rich semantic information, they lack sufficient frameworks to explicitly represent hierarchical syntactic structures. In this study, we focus on Holographic CCG (Hol-CCG), a model originally proposed outside the context of quantum theory. Hol-CCG models Combinatory Categorial Grammar (CCG)—a discrete syntactic theory—in a continuous vector space using circular correlation. Yet, the mathematical rationale for why circular correlation is suitable for representing syntactic structures has remained limited. We address this by reformulating circular correlation as a diagonalized unitary transformation on the Fourier basis, thereby interpreting it as a quantum gate. Furthermore, by analyzing performance changes under generalized basis transformations and component mixing within a quantum-generalized framework, we reveal that the syntactic representational capacity of Hol-CCG critically depends on the specific mathematical structure of diagonal phase operations in the Fourier basis.