Abstract
The laws of quantum physics mean that prominent classical cryptographic protocols can be broken using quantum computers, but they also permit security guarantees that are classically impossible. For example, quantum states cannot be cloned, which restricts the capabilities of any adversary. Here we show that uncloneable encryption exists with no computational assumptions, with security approaching the ideal value as an inverse-polynomial function of the security parameter. With this scheme, two non-interacting adversaries cannot both learn an encrypted message, even if they are both given the encryption key. Our proof uses the properties of a monogamy-of-entanglement game associated with the Haar measure encryption. Using this connection, we show that any state that succeeds with high probability cannot be close to being maximally entangled between the referee and either of the adversaries. The decoupling principle then implies that either adversary becomes completely uncorrelated and, therefore, cannot win significantly better than random guessing.
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Acknowledgements
We are grateful to A. Broadbent for insightful discussions and helpful comments on a draft of the paper. A.B. thanks D. Leung for teaching her about decoupling. E.C. thanks everyone with whom he has discussed the uncloneable encryption problem in depth: P. Botteron, S. Kundu, S. Lord, A. Mehta, I. Nechita, M. Nevins, C. Pellegrini, D. Rochette, H. Salmasian and W. Slofstra. Research at the Perimeter Institute is supported in part by the Government of Canada through the Department of Innovation, Science, and Economic Development Canada and by the Province of Ontario through the Ministry of Colleges and Universities. E.C. is supported by a CGS D scholarship from NSERC.
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Bhattacharyya, A., Culf, E. Uncloneable encryption from decoupling. Nat. Phys. 22, 315–318 (2026). https://doi.org/10.1038/s41567-025-03154-7
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DOI: https://doi.org/10.1038/s41567-025-03154-7
