Diagonal Unitary Covariant Superchannels
Abstract
We present a complete characterization of diagonal unitary covariant (DU-covariant) superchannels, i.e. higher-order transformations transforming quantum channels into themselves. Necessary and sufficient conditions for complete positivity and trace preservation are derived and the canonical decomposition describing DU-covariant superchannels is provided. The presented framework unifies and extends known families of covariant quantum channels and enables explicit analysis of their action on physically relevant examples, including amplitude-damping, bit-flip, and Pauli channels. Our results provide a practical toolbox for symmetry-restricted higher-order quantum processes and offer a setting for exploring open problems such as the celebrated PPT conjecture.
Cite
@article{arxiv.2512.24389,
title = {Diagonal Unitary Covariant Superchannels},
author = {Dariusz Chruściński and Vivek Pandey and Sohail},
journal= {arXiv preprint arXiv:2512.24389},
year = {2026}
}
Comments
34 pages, no figures