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PreprintarXiv licencearXiv

No linear stretching of single-copy quantum pseudorandomness

Abstract

Pseudorandom states, introduced by Ji, Liu, and Song (CRYPTO 2018), are quantum analogues of classical pseudorandom generators. A fundamental property of classical pseudorandom generators is that their output can be stretched to arbitrary polynomial length. Whether an analogous stretching property holds for quantum pseudorandom states has been elusive. Here, we essentially resolve this question for the single-copy variant of pseudorandom states, 1PRS. We show, via a unitary oracle separation, that no fully black-box construction can stretch the output length of a 1PRS by any constant factor greater than one.

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BibTeX
@misc{chen2026linear,
  title = {{No linear stretching of single-copy quantum pseudorandomness}},
  author = {Boyang Chen and Andrea Coladangelo and Yao-Ting Lin and Nikos Skoumios and Justin Tysdal and Yiming Wang},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2606.24736},
  eprint = {2606.24736},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2606.24736},
}
RIS
TY  - UNPB
TI  - No linear stretching of single-copy quantum pseudorandomness
AU  - Boyang Chen
AU  - Andrea Coladangelo
AU  - Yao-Ting Lin
AU  - Nikos Skoumios
AU  - Justin Tysdal
AU  - Yiming Wang
PY  - 2026
DA  - 2026/10/05
PB  - arXiv
DO  - 10.48550/arxiv.2606.24736
UR  - https://arxiv.org/abs/2606.24736
AB  - Pseudorandom states, introduced by Ji, Liu, and Song (CRYPTO 2018), are quantum analogues of classical pseudorandom generators. A fundamental property of classical pseudorandom generators is that their output can be stretched to arbitrary polynomial length. Whether an analogous stretching property holds for quantum pseudorandom states has been elusive. Here, we essentially resolve this question for the single-copy variant of pseudorandom states, 1PRS. We show, via a unitary oracle separation, that no fully black-box construction can stretch the output length of a 1PRS by any constant factor greater than one.
ER  -