Robust classical and quantum communication over almost-iid channels
Abstract
The independent and identically distributed (iid) paradigm for asymptotic communication through quantum channels describes n uses of a channel Φ by Φ⊗ n. Since exact tensor-power behaviour is an idealization, we ask whether the asymptotic capacities of Φ remain achievable for channel sequences that are almost-iid along Φ. We consider sequences of Choi-almost-iid channels whose normalized Choi states are Mazzola-Sutter-Renner (MSR) almost-iid along the normalized Choi state of Φ, with defect parameters rn=o(n). In Renner's exponential de Finetti theorem for quantum states, almost-iid states appear in the approximating mixture and motivate the MSR almost-iid class. Choi-almost-iid channels play the corresponding role in an exponential de Finetti theorem for quantum channels established in a companion paper. In this paper, we prove that the universal unassisted classical and quantum capacities of the class of Choi-almost-iid channels along Φ equal those of the channel Φ. Here universality is within this class: for each rate below the relevant capacity, a code sequence depending on Φ and the rate, but not on the particular channel sequence, achieves vanishing error for every sequence in the class.
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BibTeX
@misc{ye2026robust,
title = {{Robust classical and quantum communication over almost-iid channels}},
author = {Liuhang Ye and Bjarne Bergh and Nilanjana Datta},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.00442},
eprint = {2610.00442},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.00442},
}
RIS
TY - UNPB
TI - Robust classical and quantum communication over almost-iid channels
AU - Liuhang Ye
AU - Bjarne Bergh
AU - Nilanjana Datta
PY - 2026
DA - 2026/10/01
PB - arXiv
DO - 10.48550/arxiv.2610.00442
UR - https://arxiv.org/abs/2610.00442
AB - The independent and identically distributed (iid) paradigm for asymptotic communication through quantum channels describes n uses of a channel Φ by Φ^⊗ n. Since exact tensor-power behaviour is an idealization, we ask whether the asymptotic capacities of Φ remain achievable for channel sequences that are almost-iid along Φ. We consider sequences of Choi-almost-iid channels whose normalized Choi states are Mazzola-Sutter-Renner (MSR) almost-iid along the normalized Choi state of Φ, with defect parameters r_n=o(n). In Renner's exponential de Finetti theorem for quantum states, almost-iid states appear in the approximating mixture and motivate the MSR almost-iid class. Choi-almost-iid channels play the corresponding role in an exponential de Finetti theorem for quantum channels established in a companion paper. In this paper, we prove that the universal unassisted classical and quantum capacities of the class of Choi-almost-iid channels along Φ equal those of the channel Φ. Here universality is within this class: for each rate below the relevant capacity, a code sequence depending on Φ and the rate, but not on the particular channel sequence, achieves vanishing error for every sequence in the class.
ER -