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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.

Our summary of the paper, in our own words — not its text. The work belongs to its authors; read it at the links above.

 Institutions

 Fields, topics and concepts

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.

The paper itself, not this page. BibTeX from the library's record of the work. DOI 10.18653/v1/2026.findings-acl.522

@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}
}

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