,
Minbo Gao
,
Tongyang Li
,
Qisheng Wang
,
Xinzhao Wang
Creative Commons Attribution 4.0 International license
We propose a quantum multi-level estimation framework for a functional ∑_{i=1}^n f(p_i) of a discrete distribution (p_i)_{i=1}^n. We partition the values p_i into logarithmically many intervals whose length decays exponentially. For each interval, we perform non-destructive singular value discrimination to isolate the relevant p_i, enabling adaptive estimation of the partial sum over this interval. Unlike previous variable-time approaches, our method avoids high control overhead and requires only constant extra ancilla qubits. As an application, we present efficient quantum estimators for the q-Tsallis entropy of discrete distributions. Specifically,
- For q > 1, we obtain a near-optimal quantum algorithm with query complexity Θ̃(1/ε^{max{1/(2(q-1)), 1}}), improving the prior best O(1/ε^{1+1/(q-1)}) due to Liu and Wang (SODA 2025; IEEE Trans. Inf. Theory 2026).
- For 0 < q < 1, we obtain a quantum algorithm with query complexity Õ(n^{1/q-1/2}/ε^{1/q}), exhibiting a quantum speedup over the near-optimal classical estimators due to Jiao, Venkat, Han, and Weissman (IEEE Trans. Inf. Theory 2017). Our results achieve, to our knowledge, the first near-optimal quantum estimators for parameterized q-entropy for non-integer q.
@InProceedings{chen_et_al:LIPIcs.ICALP.2026.58,
author = {Chen, Kean and Gao, Minbo and Li, Tongyang and Wang, Qisheng and Wang, Xinzhao},
title = {{Quantum Multi-Level Estimation of Functionals of Discrete Distributions}},
booktitle = {53rd International Colloquium on Automata, Languages, and Programming (ICALP 2026)},
pages = {58:1--58:23},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-428-4},
ISSN = {1868-8969},
year = {2026},
volume = {374},
editor = {Bhattacharya, Sayan and Nanongkai, Danupon and Benedikt, Michael and Puppis, Gabriele},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2026.58},
URN = {urn:nbn:de:0030-drops-264473},
doi = {10.4230/LIPIcs.ICALP.2026.58},
annote = {Keywords: Quantum algorithms, functional estimation, entropy estimation, query complexity, Tsallis entropy}
}