# Advances in quantum dense coding

## TL;DR

This paper reviews the theoretical foundations, experimental progress, and future directions of quantum dense coding, a key quantum communication protocol that enhances information transfer using quantum resources.

## Contribution

It provides a comprehensive overview of the development, experimental implementations, and potential future advancements in quantum dense coding.

## Key findings

- Progress in photonic qubits and qudits implementations
- Advancements in optical modes and nuclear magnetic resonance experiments
- Discussion of future research directions in quantum dense coding

## Abstract

Quantum dense coding is one of the most important protocols in quantum communication. It derives from the idea of using quantum resources to boost the communication capacity and now serves as a key primitive across a variety of quantum information protocols. Here, we focus on the basic theoretical ideas behind quantum dense coding, discussing its development history from discrete and continuous variables to quantum networks, then to its variant protocols and applications in quantum secure communication. With this basic background in hand, we then review the main experimental achievements, from photonic qubits and qudits to optical modes, nuclear magnetic resonance, and atomic systems. Besides the state of the art, we finally discuss potential future steps.