# Comment on "Conditional Decoupling of Quantum Information"

## TL;DR

This paper critiques a recent claim about a new extension of the decoupling approach in quantum information theory, providing an alternative proof that challenges the original assertion.

## Contribution

It offers an alternative proof for the main result of Berta et al., showing that their claimed novelty is unwarranted and clarifying the conceptual understanding.

## Key findings

- The original claim of a new extension is challenged.
- An alternative proof using standard decoupling is provided.
- The claim of conceptual novelty is deemed unwarranted.

## Abstract

Berta et al [Phys. Rev. Lett., 121, 040504 (2018)] claim that their result provides a conceptually new extension of the decoupling approach to quantum information theory. We provide an alternate proof using the plain-vanilla decoupling approach for the achievable rates of their main result and hence, their claim is unwarranted, and the title can be misleading when taken in conjunction with the claim.