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Journal of Chemical Theory and Computation

Bridging the Gap between Transformer-Based Neural Networks and Tensor Networks for Quantum Chemistry

Bowen Kan, Yingqi Tian, Yangjun Wu, Yunquan Zhang, Honghui Shang

Published Mar 2, 2025• 7 citations
Publisher

Abstract

The neural network quantum state (NNQS) method has demonstrated promising results in ab initio quantum chemistry, achieving remarkable accuracy in molecular systems. However, efficient calculation of systems with large active spaces remains challenging. This study introduces a novel approach that bridges tensor network states with the transformer-based NNQS-Transformer (QiankunNet) to enhance accuracy and convergence for systems with relatively large active spaces. By transforming tensor network states into active space configuration interaction type wave functions, QiankunNet achieves accuracy surpassing both the pretraining density matrix renormalization group (DMRG) results and traditional coupled cluster methods, particularly in strongly correlated regimes. We investigate two configuration transformation methods: the sweep-based direct conversion (Conv.) method and the entanglement-driven genetic algorithm (EDGA) method, with Conv. showing superior efficiency. The effectiveness of this approach is validated on H 2 O with a large active space (10e, 24o) in the cc-pVDZ basis set, demonstrating an efficient routine between DMRG and QiankunNet and also offering a promising direction for advancing quantum state representation in complex molecular systems.

DOI
10.1021/acs.jctc.4c01703

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Accurately solving the Schrödinger equation for intricate systems remains a prominent challenge in physical sciences. Here we present QiankunNet, a neural network quantum state (NNQS) framework that combines Transformer architectures with efficient autoregressive sampling to solve the many-electron Schrödinger equation. At its core is a Transformer-based wave function ansatz that captures complex quantum correlations through attention mechanisms, effectively learning the structure of many-body states. The quantum state sampling employs layer-wise Monte Carlo tree search (MCTS) that naturally enforces electron number conservation while exploring orbital configurations. The framework incorporates physics-informed initialization using truncated configuration interaction solutions, providing principled starting points for variational optimization. Our systematic benchmarks demonstrate QiankunNet's versatility across different chemical systems. For molecular systems up to 30 spin orbitals, we achieved correlation energies reaching 99.9% of the full configuration interaction (FCI) benchmark, setting a new standard for neural network quantum states. Most notably, in treating the Fenton reaction mechanism, a fundamental process in biological oxidative stress, QiankunNet successfully handled a large CAS(46e,26o) active space, enabling accurate description of the complex electronic structure evolution during Fe(II) to Fe(III) oxidation.