Order preserving maps on quantum measurements

Teiko Heinosaari, Maria Anastasia Jivulescu, Ion Nechita

Research output: Contribution to journalArticleScientificpeer-review


We study the partially ordered set of equivalence classes of quantum measurements endowed with the post-processing partial order. The post-processing order is fundamental as it enables to compare measurements by their intrinsic noise and it gives grounds to define the important concept of quantum incompatibility. Our approach is based on mapping this set into a simpler partially ordered set using an order preserving map and investigating the resulting image. The aim is to ignore unnecessary details while keeping the essential structure, thereby simplifying e.g. detection of incompatibility. One possible choice is the map based on Fisher information introduced by Huangjun Zhu, known to be an order morphism taking values in the cone of positive semidefinite matrices. We explore the properties of that construction and improve Zhu's incompatibility criterion by adding a constraint depending on the number of measurement outcomes. We generalize this type of construction to other ordered vector spaces and we show that this map is optimal among all quadratic maps.

Original languageEnglish
Article numberA5
Pages (from-to)853
Number of pages32
Publication statusPublished - 2022
MoE publication typeA1 Journal article-refereed


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