Demonstration of active routing of entanglement in a multi-user network

TL;DR

This paper demonstrates a stable, fibre-based quantum network capable of dynamically routing entanglement between multiple users using wavelength multiplexing and optical switches, with high fidelity and telecom compatibility.

Contribution

It introduces a scalable, stable entanglement distribution system with dynamic routing capabilities in a multi-user quantum network.

Findings

Entanglement fidelities up to 99% achieved.

Successful dynamic allocation of entanglement between user pairs.

System is fibre and waveguide based for stability and integration.

Abstract

We implement an entanglement distribution network based on wavelength-multiplexing and optical switching for quantum communication applications. Using a high-brightness source based on spontaneous parametric down-conversion in periodically-poled lithium niobate waveguides, we generate polarisation entangled photon pairs with a broad spectrum covering the telecom wavelengths around 1550nm. The photon pairs have entanglement fidelities up to 99%, and are distributed via passive wavelength multiplexing in a static multi-user network. We furthermore demonstrate a possible network application in a scenario with a single centralised source dynamically allocating two-party entanglement to any pair of users by means of optical switches. The whole system, from the pump laser up to the receivers, is fibre and waveguide based, resulting in maximal stability, minimal losses and the advantage of readily integrable telecom components in the 1550nm range.