HVIA: A Hybrid Variational Ising Architecture for Quantum Language Modeling
Chengang Mao, Haisheng Li
Abstract
Abstract Language modeling in natural language processing has predominantly relied on large-scale classical neural architectures, yet constructing expressive and resource-efficient models compatible with Noisy Intermediate-Scale Quantum (NISQ) devices remains a fundamental open challenge. In this work, two Ising-inspired variational quantum-classical architectures are proposed to enhance representational capacity by leveraging spin-coupling mechanisms and Ising-type Hamiltonian evolution within hybrid classical-quantum layers. Specifically, a quantum Ising Ansatz circuit parameterized by an Ising Hamiltonian is constructed, and a quantum approximate optimization algorithm (QAOA) is incorporated to reduce the number of trainable circuit parameters while enabling learnable quantum evolution of hidden states. To achieve stable and efficient hybrid training under NISQ constraints, a joint optimization strategy is introduced that combines the Adam optimizer with quantum simultaneous perturbation stochastic approximation (SPSA), yielding convergence acceleration of up to $64\%$ relative to parameter-shift rule and Adam-only baselines. Empirical evaluations on the WikiText-2 benchmark demonstrate that the proposed architectures effectively capture long-range semantic dependencies, achieving a competitive perplexity of $\text{PPL} = 39.8$ (lower values indicate stronger language modeling performance). This result surpasses existing quantum language models, including Quixer, Quantum LSTM, and Quantum GRU, and approaches the performance of the classical NanoGPT baseline ($\text{PPL} = 40.5$). Collectively, these findings establish the viability of Ising-based hybrid quantum-classical networks as a promising direction for practical quantum natural language processing.