Entanglement distribution over 150 km in wavelength division multiplexed channels for quantum cryptography

TL;DR

This paper demonstrates the distribution of high-quality entanglement over 150 km using wavelength division multiplexing, significantly improving secret key rates for quantum cryptography with scalable and practical technology.

Contribution

It introduces a scalable wavelength multiplexing approach for long-distance entanglement distribution, enhancing secret key rates and paving the way for real-world quantum cryptography applications.

Findings

Entanglement distributed over 150 km fiber link.

Coincidence rates scale linearly with channels, outperforming previous work.

System is compatible with device-independent quantum cryptography.

Abstract

Granting information privacy is of crucial importance in our society, notably in fiber communication networks. Quantum cryptography provides a unique means to establish, at remote locations, identical strings of genuine random bits, with a level of secrecy unattainable using classical resources. However, several constraints, such as non-optimized photon number statistics and resources, detectors' noise, and optical losses, currently limit the performances in terms of both achievable secret key rates and distances. Here, these issues are addressed using an approach that combines both fundamental and off-the-shelves technological resources. High-quality bipartite photonic entanglement is distributed over a 150 km fiber link, exploiting a wavelength demultiplexing strategy implemented at the end-user locations. It is shown how coincidence rates scale linearly with the number of employed telecommunication channels, with values outperforming previous realizations by almost one order of magnitude. Thanks to its potential of scalability and compliance with device-independent strategies, this system is ready for real quantum applications, notably entanglement-based quantum cryptography.