Robustness-based bounds for approximate joint realizations of incompatible quantum channels
Abstract
Several quantum channels may fail to admit an exact joint realization, a property known as incompatibility. Channel incompatibility unifies various quantum limitations, such as measurement uncertainty, the no-information-without-disturbance principle, and the no-cloning and no-broadcasting theorems. We address how accurately incompatible channels can be approximated by the marginals of a single joint channel, quantified by the minimum total diamond-norm error over all joint realizations. We establish two-sided bounds relating it to the generalized robustness of incompatibility (RoI), a noise-based resource quantifier of incompatibility. For identity channels, we determine both the RoI and the minimum total error exactly. The upper bound is attained by the optimal symmetric universal cloner, while the prefactor in the lower bound is asymptotically optimal as the dimension tends to infinity. Applying this result to measurement channels provides a unified, model-independent framework encompassing error-error and information-error-disturbance tradeoffs. Furthermore, our robustness-based evaluation of disturbance outperforms an algebraic bound for every non-trivial POVM in dimensions up to six.
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BibTeX
@misc{minagawa2026robustnessbased,
title = {{Robustness-based bounds for approximate joint realizations of incompatible quantum channels}},
author = {Shintaro Minagawa and Ryo Takakura and Kensei Torii},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2605.11924},
eprint = {2605.11924},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.11924},
}
RIS
TY - UNPB
TI - Robustness-based bounds for approximate joint realizations of incompatible quantum channels
AU - Shintaro Minagawa
AU - Ryo Takakura
AU - Kensei Torii
PY - 2026
DA - 2026/09/30
PB - arXiv
DO - 10.48550/arxiv.2605.11924
UR - https://arxiv.org/abs/2605.11924
AB - Several quantum channels may fail to admit an exact joint realization, a property known as incompatibility. Channel incompatibility unifies various quantum limitations, such as measurement uncertainty, the no-information-without-disturbance principle, and the no-cloning and no-broadcasting theorems. We address how accurately incompatible channels can be approximated by the marginals of a single joint channel, quantified by the minimum total diamond-norm error over all joint realizations. We establish two-sided bounds relating it to the generalized robustness of incompatibility (RoI), a noise-based resource quantifier of incompatibility. For identity channels, we determine both the RoI and the minimum total error exactly. The upper bound is attained by the optimal symmetric universal cloner, while the prefactor in the lower bound is asymptotically optimal as the dimension tends to infinity. Applying this result to measurement channels provides a unified, model-independent framework encompassing error-error and information-error-disturbance tradeoffs. Furthermore, our robustness-based evaluation of disturbance outperforms an algebraic bound for every non-trivial POVM in dimensions up to six.
ER -