Large Language Models Can Help Mitigate Barren Plateaus in Quantum Neural Networks
Paper · 2026 · Jun Zhuang and Chaowen Guan
Summary
Quantum neural networks (QNNs) are often untrainable because of barren plateaus (BPs). At initialization, gradient variance shrinks exponentially as qubits are added, so gradient-based optimizers stall almost immediately. Existing initialization fixes, such as GaInit and BeInit, sample parameters once from a fixed, hand-designed distribution. That approach relies on idealized assumptions and does not adapt to circuit size or data.
The authors propose AdaInit, a loop in which an LLM proposes candidate initial parameters. Its prompts include a dataset description and feedback on earlier gradient behaviour. Each candidate initializes a QNN that is trained briefly, and the resulting early gradient variance is scored with Expected Improvement. The prompts, the best variance so far and a pool of good candidates are then updated.
The authors model this loop as a submartingale. Using Doob's convergence and stopping-time results, they prove it almost surely finds parameters with non-negligible gradient variance in finite time. Experiments show AdaInit keeps gradient variance higher than baselines as QNNs grow, which positions LLMs as adaptive initializers for quantum models.
Key points
- Theory: The paper proves a supremum and an expected hitting time for the iterative process. It assumes bounded gradients, meaning no gradient explosion occurs.
- Baselines: AdaInit is compared with three classic initialization methods and two BP-oriented strategies, GaInit and BeInit.
- Model sizes: Simulations cover QNNs with 2–20 qubits and 4–40 layers, under noise-free measurement.
- Datasets: The experiments use the Iris, Wine, Titanic and MNIST benchmarks.
- Limitations: BPs caused by the ansatz itself are out of scope. Future work targets faster convergence and using the framework to guide QNN architecture design.
Institutions
Fields, topics and concepts
📚 Shelves 4The field of science this work belongs to (OpenAlex fields).Computer Science · 18,614 worksArtificial Intelligence · 17,965 worksPhysics and Astronomy · 52 worksAtomic and Molecular Physics, and Optics · 4 works
🧭 Topics 1Research subjects and languages the work is about.Language models & pretraining · 3,894 works
Cite
Cite as Jun Zhuang and Chaowen Guan. 2026. Large Language Models Can Help Mitigate Barren Plateaus in Quantum Neural Networks. Findings of the Association for Computational Linguistics: ACL 2026.
@inproceedings{zhuang2026large,
title = {{Large Language Models Can Help Mitigate Barren Plateaus in Quantum Neural Networks}},
author = {Jun Zhuang and Chaowen Guan},
booktitle = {Findings of the Association for Computational Linguistics: ACL 2026},
year = {2026},
doi = {10.18653/v1/2026.findings-acl.522},
url = {https://doi.org/10.18653/v1/2026.findings-acl.522}
}References
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