# Skew informations from an operational view via resource theory of asymmetry

## TL;DR

This paper provides an operational perspective on skew informations in quantum resource theory, establishing their physical meaning, proving superadditivity limitations, and applying results to distributed quantum clocks.

## Contribution

It offers a new operational interpretation of generalized skew informations and proves their non-superadditivity, confirming a conjecture for Wigner-Yanase skew information.

## Key findings

- Skew informations are valid asymmetry resource monotones.
- No skew information can be superadditive.
- A weaker superadditivity relation is established.

## Abstract

The Wigner-Yanase skew information was proposed to quantify the information contained in quantum states with respect to a conserved additive quantity, and it was later extended to the Wigner-Yanase-Dyson skew informations. Recently, the Wigner-Yanase-Dyson skew informations have been recognized as valid resource measures for the resource theory of asymmetry, and their properties have been investigated from a resource-theoretic perspective. The Wigner-Yanse-Dyson skew informations have been further generalized to a class called metric-adjusted skew informations, and this general family of skew informations have also been found to be valid asymmetry monotones. Here, we analyze this general family of the skew informations from an operational point of view by utilizing the fact that they are valid asymmetry resource monotones. We show that such an approach allows for clear physical meanings as well as simple proofs of some of the basic properties of the skew informations. Notably, we constructively prove that any type of skew information cannot be superadditive, where the violation of the superadditivity had been only known for a specific class of skew informations with numerical counterexamples. We further show a weaker version of superadditivity relation applicable to the general class of the skew informations, which proves a conjecture made for the Wigner-Yanase skew information as a special case. We finally discuss an application of our results for a situation where quantum clocks are distributed to multiple parties.