,
Soumik Ghosh,
Makrand Sinha,
Henry Yuen
Creative Commons Attribution 4.0 International license
We show that concrete hardness assumptions about learning or cloning the output state of a random quantum circuit can be used as the foundation for secure quantum cryptography. In particular, under these assumptions we construct secure one-way state generators (OWSGs), digital signature schemes, quantum bit commitments, and private key encryption schemes. We also discuss evidence for these hardness assumptions by analyzing the best-known quantum learning algorithms, as well as proving black-box lower bounds for cloning and learning given state preparation oracles.
Our random circuit-based constructions provide concrete instantiations of quantum cryptographic primitives whose security do not depend on the existence of one-way functions. The use of random circuits in our constructions also opens the door to {NISQ-friendly quantum cryptography}. We discuss noise tolerant versions of our OWSG and digital signature constructions which can potentially be implementable on noisy quantum computers connected by a quantum network. On the other hand, they are still secure against {noiseless} quantum adversaries, raising the intriguing possibility of a useful implementation of an end-to-end cryptographic protocol on near-term quantum computers. Finally, our explorations suggest that the rich interconnections between learning theory and cryptography in classical theoretical computer science also extend to the quantum setting.
@InProceedings{fefferman_et_al:LIPIcs.ITCS.2026.56,
author = {Fefferman, Bill and Ghosh, Soumik and Sinha, Makrand and Yuen, Henry},
title = {{The Hardness of Learning Quantum Circuits and Its Cryptographic Applications}},
booktitle = {17th Innovations in Theoretical Computer Science Conference (ITCS 2026)},
pages = {56:1--56:21},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-410-9},
ISSN = {1868-8969},
year = {2026},
volume = {362},
editor = {Saraf, Shubhangi},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2026.56},
URN = {urn:nbn:de:0030-drops-253431},
doi = {10.4230/LIPIcs.ITCS.2026.56},
annote = {Keywords: quantum learning, quantum circuits, cryptographic hardness, one-way state generators}
}