# On the upper bound of classical correlations in a bipartite quantum system

## TL;DR

This paper establishes an upper bound on classical correlations in bipartite quantum systems, providing a simpler proof that does not rely on correlation matrices, thereby enhancing understanding of quantum discord.

## Contribution

It offers a shorter, more transparent proof of the upper bound on classical correlations in bipartite quantum systems, avoiding the use of correlation matrices.

## Key findings

- Classical correlations are bounded by the minimum of subsystem entropies.
- The proof simplifies previous approaches to bounding quantum discord.
- Provides clearer insight into the structure of quantum correlations.

## Abstract

For a bipartite quantum system consisting of subsystems A and B it was shown by Zhang et al. (Physics Letters A 376 (2012) 3588-3592) that the amount of classical correlations, which is used to define the quantum discord, is known to be bounded from above by the minimum of the von Neumann entropies of the subsystems A and B. We provide an alternative proof that is shorter and more transparent as it works without defining correlation matrices.