Generalised Entropy Accumulation


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Date

2024-11

Publication Type

Journal Article

ETH Bibliography

yes

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Abstract

Consider a sequential process in which each step outputs a system Ai and updates a side information register E. We prove that if this process satisfies a natural “non-signalling” condition between past outputs and future side information, the minentropy of the outputs A1,..., An conditioned on the side information E at the end of the process can be bounded from below by a sum of von Neumann entropies associated with the individual steps. This is a generalisation of the entropy accumulation theorem (EAT) (Dupuis et al. in Commun Math Phys 379: 867–913, 2020), which deals with a more restrictive model of side information: there, past side information cannot be updated in subsequent rounds, and newly generated side information has to satisfy a Markov condition. Due to its more general model of side-information, our generalised EAT can be applied more easily and to a broader range of cryptographic protocols. As examples, we give the first multi-round security proof for blind randomness expansion and a simplified analysis of the E91 QKD protocol. The proof of our generalised EAT relies on a new variant of Uhlmann’s theorem and new chain rules for the Rényi divergence and entropy, which might be of independent interest.

Publication status

published

Editor

Book title

Volume

405 (11)

Pages / Article No.

261

Publisher

Springer

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Organisational unit

03781 - Renner, Renato / Renner, Renato check_circle

Notes

Funding

185902 - QSIT - Quantum Science and Technology (SNF)
188541 - Information-theoretic limits to time measurements (SNF)

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