# Orbital angular momentum states enabling fiber-based high-dimensional quantum communication

## TL;DR

This paper demonstrates the reliable transmission of high-dimensional quantum states using orbital angular momentum modes in a fiber, enabling advanced quantum communication protocols over 1.2 km.

## Contribution

It shows how a novel air-core fiber can faithfully transmit D-dimensional OAM states, advancing high-dimensional quantum communication technology.

## Key findings

- High-fidelity transmission of 4 OAM quantum states in fiber
- Implementation of three quantum key distribution protocols
- Successful propagation of superpositions of OAM states

## Abstract

Quantum networks are the ultimate target in quantum communication, where many connected users can share information carried by quantum systems. The keystones of such structures are the reliable generation, transmission and manipulation of quantum states. Two-dimensional quantum states, qubits, are steadily adopted as information units. However, high-dimensional quantum states, qudits, constitute a richer resource for future quantum networks, exceeding the limitations imposed by the ubiquitous qubits. The generation and manipulation of such $D$-level systems have been improved over the last ten years, but their reliable transmission between remote locations remains the main challenge. Here, we show how a recent air-core fiber supporting orbital angular momentum (OAM) modes can be exploited to faithfully transmit $D$-dimensional states. Four OAM quantum states and their superpositions are created, propagated in a 1.2 km long fiber and detected with high fidelities. In addition, three quantum key distribution (QKD) protocols are implemented as concrete applications to assert the practicality of our results. This experiment enhances the distribution of high-dimensional quantum states, attesting the orbital angular momentum as vessel for the future quantum network.