Synchronized distribution of quantum entanglement coexisting with high-rate, broadband classical optical communications over a real-world fiber link

TL;DR

This paper demonstrates the coexistence of quantum entanglement distribution with high-rate classical optical communications over a real-world fiber link, achieving record classical bandwidth and power levels while maintaining quantum fidelity.

Contribution

It presents the first implementation of entanglement-based quantum communication coexisting with high-capacity classical traffic over the same fiber link.

Findings

Quantum entanglement maintained with high fidelity alongside 36 Tbps classical transmission.

Successful coexistence at 21.4-dBm aggregate power with optimized wavelength filtering.

Record classical bandwidth of 800 Gbps channels in a real-world fiber environment.

Abstract

Compatibility with existing classical network infrastructure offers a scalable path towards deploying largescale quantum networks. Here, we demonstrate O-band polarization-encoded quantum entanglement distribution over an installed 24.4-km fiber while coexisting with a state-of-the-art fully-loaded C-band classical communications line system and a picosecond-level precision L-band synchronization signal. The classical system carries two 800-Gbps channels while the remainder of the C-band is filled with amplified spontaneous emission as is standard for such state-of-the-art communications systems. We examine the spontaneous Raman scattering spectrum generated from this broadband C-band light and offer insights into wavelength allocation for O-band quantum channels. Optimal wavelength selection and narrow filtering enable well-preserved Bell state fidelity when coexisting with 21.4-dBm aggregate launch power across the C-band suitable for 36 Tbps transmission. To the best of our knowledge, this is the first implementation of entanglement-based quantum communications between two remote nodes coexisting with independent classical communications traffic. We demonstrate coexistence of quantum entanglement with ultra-high power levels and record classical bandwidth, offering promise for real-world entanglement-based networking integrated within high-capacity communications infrastructure.