,
Supartha Podder
Creative Commons Attribution 4.0 International license
Aaronson, Bouland, Fitzsimons and Lee [Scott Aaronson et al., 2014] introduced the complexity class PDQP (which was original labeled naCQP), an alteration of BQP enhanced with the ability to obtain non-collapsing measurements, samples of quantum states without collapsing them. Although SZK ⊆ PDQP, it still requires Ω(N^(1/4)) queries to solve unstructured search. We formulate an alternative equivalent definition of PDQP, which we use to prove the positive weighted adversary lower-bounding method, establishing multiple tighter bounds and a trade-off between queries and non-collapsing measurements. We utilize the technique in order to analyze the query complexity of the well-studied majority and element distinctness problems. Additionally, we prove a tight Θ(N^(1/3)) bound on search. Furthermore, we use the lower-bound to explore PDQP under query restrictions, finding that when combined with non-adaptive queries, we limit the speed-up in several cases.
@InProceedings{miloschewsky_et_al:LIPIcs.CCC.2025.12,
author = {Miloschewsky, David and Podder, Supartha},
title = {{New Lower-Bounds for Quantum Computation with Non-Collapsing Measurements}},
booktitle = {40th Computational Complexity Conference (CCC 2025)},
pages = {12:1--12:23},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-379-9},
ISSN = {1868-8969},
year = {2025},
volume = {339},
editor = {Srinivasan, Srikanth},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CCC.2025.12},
URN = {urn:nbn:de:0030-drops-237067},
doi = {10.4230/LIPIcs.CCC.2025.12},
annote = {Keywords: Non-collapsing measurements, Quantum lower-bounds, Quantum adversary method}
}