# Coexistence of entanglement-based quantum channels with DWDM classical channels over hollow core fibre in a four node quantum communication network

## TL;DR

This paper shows how quantum and classical communication can coexist in a fiber network, maintaining high performance over long distances.

## Contribution

The novel contribution is demonstrating coexistence of entanglement-based quantum and classical channels in a multi-node network using hollow core fiber.

## Key findings

- Three quantum channels coexist with 800 Gbps classical channels over 11.5 km hollow core fiber.
- Quantum key distribution achieved Bell state fidelity of up to 90.0 ± 0.8%.
- Secret key rates remained stable for 55 hours in a four-node quantum network.

## Abstract

We experimentally demonstrate the coexistence of three entanglement-based quantum channels with carrier-grade classical optical channels over 11.5 km hollow core nested antiresonant nodeless fibre, in a four user quantum network. A transmission of 800 Gbps is achieved with four classical channels simultaneously with three quantum channels all operating in the C-band with a separation of 1.2 nm, with aggregated coexistence power of −3 dBm. We established quantum key distribution in the four-node full-mesh quantum network with Bell state fidelity of up to 90.0 ± 0.8%. The secret key rate for all the links in the network are passively preserved over 55 hours of experimental time.