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Main Authors: Hao, Zihan, Huang, Zikuan, Liu, Qipeng
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2602.23763
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author Hao, Zihan
Huang, Zikuan
Liu, Qipeng
author_facet Hao, Zihan
Huang, Zikuan
Liu, Qipeng
contents In this work, we establish the first separation between computation with bounded and unbounded space, for problems with short outputs (i.e., working memory can be exponentially larger than output size), both in the classical and the quantum setting. Towards that, we introduce a problem called nested collision finding, and show that optimal query complexity can not be achieved without exponential memory. Our result is based on a novel ``two-oracle recording'' technique, where one oracle ``records'' the computation's long outputs under the other oracle, effectively reducing the time-space trade-off for short-output problems to that of long-output problems. We believe this technique will be of independent interest for establishing time-space tradeoffs in other short-output settings.
format Preprint
id arxiv_https___arxiv_org_abs_2602_23763
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On the Need for (Quantum) Memory with Short Outputs
Hao, Zihan
Huang, Zikuan
Liu, Qipeng
Computational Complexity
In this work, we establish the first separation between computation with bounded and unbounded space, for problems with short outputs (i.e., working memory can be exponentially larger than output size), both in the classical and the quantum setting. Towards that, we introduce a problem called nested collision finding, and show that optimal query complexity can not be achieved without exponential memory. Our result is based on a novel ``two-oracle recording'' technique, where one oracle ``records'' the computation's long outputs under the other oracle, effectively reducing the time-space trade-off for short-output problems to that of long-output problems. We believe this technique will be of independent interest for establishing time-space tradeoffs in other short-output settings.
title On the Need for (Quantum) Memory with Short Outputs
topic Computational Complexity
url https://arxiv.org/abs/2602.23763