# Quantum discord-breaking and discord-annihilating channels

## TL;DR

This paper characterizes quantum discord-breaking channels acting on subsystem B and introduces discord-annihilating channels that globally destroy quantum discord, providing a comprehensive understanding of discord dynamics.

## Contribution

It completes the characterization of discord-breaking channels by including those acting on B and introduces the novel concept of discord-annihilating channels with explicit operational forms.

## Key findings

- Characterization of discord-breaking channels on subsystem B
- Introduction of discord-annihilating channels with closed-form description
- Operational interpretation involving subspace projections and state preparation

## Abstract

Quantum discord-breaking channels were previously defined as the local channels that act on subsystem $A$ to produce classical-quantum states across system $AB$. However, unlike entanglement, discord is asymmetric. Here, we characterise the discord-breaking channels that act on subsystem $B$, thus completing the overall description of discord-breaking channels. We then introduce the notion of discord-annihilating channels, which act globally on system $AB$ to destroy quantum discord, and find their closed form. Discord-annihilating channels have clear operational description, involving subspace projections on subsystem $A$ and conditional preparation of fixed states on subsystem $B$.