On the Complexity of Level-Synchronized Tree Automata for Quantum Circuit Verification
Abstract
Reliable quantum computation requires methods for verifying quantum circuits. Level-synchronized tree automata (LSTAs) were recently introduced to represent sets of quantum states for this purpose. We study LSTAs along two axes relevant to verification: the complexity of their decision problems and the size of their representations under circuit operations. We prove that acyclic LSTAs have NP-complete nonemptiness and Π2P-complete language inclusion, and that general language inclusion is EXPSPACE-complete. We further prove inherent quadratic representation growth under individual quantum gates in a fixed qubit order, and give an adjacent-qubit reordering construction that preserves level synchronization. These results clarify the scope of applicability of the automata-theoretic toolbox for quantum circuit verification.
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BibTeX
@misc{blondin2026complexity,
title = {{On the Complexity of Level-Synchronized Tree Automata for Quantum Circuit Verification}},
author = {Michael Blondin and Samy Chady Khoumsi-Kasmi and Guillermo A. Pérez and Marnix Suilen},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.25138},
eprint = {2610.25138},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.25138},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - On the Complexity of Level-Synchronized Tree Automata for Quantum Circuit Verification
AU - Michael Blondin
AU - Samy Chady Khoumsi-Kasmi
AU - Guillermo A. Pérez
AU - Marnix Suilen
PY - 2026
DA - 2026/10/18
PB - arXiv
DO - 10.48550/arxiv.2610.25138
UR - https://arxiv.org/abs/2610.25138
AB - Reliable quantum computation requires methods for verifying quantum circuits. Level-synchronized tree automata (LSTAs) were recently introduced to represent sets of quantum states for this purpose. We study LSTAs along two axes relevant to verification: the complexity of their decision problems and the size of their representations under circuit operations. We prove that acyclic LSTAs have NP-complete nonemptiness and Π_2^P-complete language inclusion, and that general language inclusion is EXPSPACE-complete. We further prove inherent quadratic representation growth under individual quantum gates in a fixed qubit order, and give an adjacent-qubit reordering construction that preserves level synchronization. These results clarify the scope of applicability of the automata-theoretic toolbox for quantum circuit verification.
ER -