The Hilbert-Schmidt norms of quantum channels and matrix integrals over the unit sphere

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Hauptverfasser: Li, Yuan, Chen, Zhengli, Guo, Zhihua, Pang, Yongfeng
Format: Preprint
Veröffentlicht: 2026
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_version_ 1866909992091648000
author Li, Yuan
Chen, Zhengli
Guo, Zhihua
Pang, Yongfeng
author_facet Li, Yuan
Chen, Zhengli
Guo, Zhihua
Pang, Yongfeng
contents The dynamics of quantum systems are generally described by a family of quantum channels (linear, completely positive and trace preserving maps). In this note, we mainly study the range of all possible values of $\|\mathcal{E}\|_2^2+\|\widetilde{\mathcal{E}}\|_2^2$ for quantum channels $\mathcal{E}$ and give the equivalent characterizations for quantum channels that achieve these maximum and minimum values, respectively, where $\|\mathcal{E}\|_2$ is the Hilbert-Schmidt norm of $\mathcal{E}$ and $\widetilde{\mathcal{E}}$ is a complementary channel of $\mathcal{E}.$ Also, we get a concrete description of completely positive maps on infinite dimensional systems preserving pure states. Moreover, the equivalency of several matrix integrals over the unit sphere is demonstrated and some extensions of these matrix integrals are obtained.
format Preprint
id arxiv_https___arxiv_org_abs_2601_10943
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle The Hilbert-Schmidt norms of quantum channels and matrix integrals over the unit sphere
Li, Yuan
Chen, Zhengli
Guo, Zhihua
Pang, Yongfeng
Quantum Physics
Mathematical Physics
The dynamics of quantum systems are generally described by a family of quantum channels (linear, completely positive and trace preserving maps). In this note, we mainly study the range of all possible values of $\|\mathcal{E}\|_2^2+\|\widetilde{\mathcal{E}}\|_2^2$ for quantum channels $\mathcal{E}$ and give the equivalent characterizations for quantum channels that achieve these maximum and minimum values, respectively, where $\|\mathcal{E}\|_2$ is the Hilbert-Schmidt norm of $\mathcal{E}$ and $\widetilde{\mathcal{E}}$ is a complementary channel of $\mathcal{E}.$ Also, we get a concrete description of completely positive maps on infinite dimensional systems preserving pure states. Moreover, the equivalency of several matrix integrals over the unit sphere is demonstrated and some extensions of these matrix integrals are obtained.
title The Hilbert-Schmidt norms of quantum channels and matrix integrals over the unit sphere
topic Quantum Physics
Mathematical Physics
url https://arxiv.org/abs/2601.10943