# Randomness certification in a quantum network with independent sources

## TL;DR

This paper certifies randomness in a quantum network using two independent entanglement sources, a key step toward secure large-scale quantum communication.

## Contribution

The work introduces a method for certifying device-independent randomness in a quantum network with multiple entanglement sources.

## Key findings

- Randomness certification is achieved in an entanglement-teleportation setup with two independent sources.
- The scalar extension method effectively bounds an eavesdropper's knowledge of shared secret bits.
- Theoretical predictions are validated using experimental data from a photonic quantum network.

## Abstract

Randomness certification is a foundational and practical aspect of quantum information science, essential for securing quantum communication protocols. Traditionally, these protocols have been implemented and validated with a single entanglement source, as in the paradigmatic Bell scenario. However, advancing these protocols to support more complex configurations involving multiple entanglement sources is key to building robust architectures and realizing large-scale quantum networks. Here, we show how to certify randomness in an entanglement-teleportation experiment, the building block of a quantum repeater displaying two independent sources of entanglement. Using the scalar extension method, we address the challenge posed by the nonconvexity of the correlation set, providing effective bounds on an eavesdropper’s knowledge of the shared secret bits. Our theoretical model characterizes the certifiable randomness within the network and is validated through the analysis of experimental data from a photonic quantum network.

Device-independent randomness is certified within a quantum network and experimentally validated on a photonic platform.