[Paper Review] Drone-based all-weather entanglement distribution

Huaying Liu, Xiao-Hui Tian+14 more|arXiv (Cornell University)|May 23, 2019

Quantum Information and Cryptography52 references20 citations

TL;DR

This paper demonstrates the first all-weather, drone-based distribution of quantum entanglement over 200 meters using compact, lightweight drones with symmetric beam apertures and single-mode fiber coupling. The experiment achieves a Clauser-Horne-Shimony-Holt (CHSH) S-parameter exceeding 2.49, validating high-fidelity entanglement under diverse weather conditions with a total take-off weight below 35 kg, enabling scalable quantum networks.

ABSTRACT

The quantum satellite is a cornerstone towards practical free-space quantum network and overcomes the photon loss over large distance. However, challenges still exist including real-time all-location coverage and multi-node construction, which may be complemented by the diversity of modern drones. Here we demonstrate the first drone-based entanglement distribution at all-weather conditions over 200 meters (test field limited), and the Clauser-Horne-Shimony-Holt S-parameter exceeds 2.49, within 35 kg take-off weight. With symmetric transmitter and receiver beam apertures and single-mode-fiber-coupling technology, such progress is ready for future quantum network with multi-node expansion. This network can be further integrated in picture-drone sizes for plug-and-play local-area coverage, or loaded onto high-altitude drones for wide-area coverage, which adds flexibility while connecting to the existing satellites and ground fiber-based quantum network.

Motivation & Objective

• To enable practical, all-weather free-space quantum communication beyond low-Earth orbit satellites.
• To overcome limitations in real-time coverage and multi-node scalability of existing quantum satellite systems.
• To develop a lightweight, portable, and weather-resilient platform for entanglement distribution using drones.
• To integrate drone-based entanglement with existing quantum networks, including satellites and fiber-based systems.
• To demonstrate feasibility of compact, symmetric optical systems for high-fidelity quantum state transfer.

Proposed method

• Utilizes a lightweight drone platform (≤35 kg take-off weight) equipped with compact, symmetric transmitter and receiver optical modules.
• Employs single-mode fiber coupling to stabilize and enhance the quality of entangled photon transmission.
• Deploys a free-space optical link with aligned beam apertures to maintain high-fidelity entanglement distribution over 200 m in varying weather conditions.
• Uses polarization-entangled photon pairs generated via spontaneous parametric down-conversion (SPDC).
• Applies real-time feedback and alignment techniques to maintain beam stability during flight and under atmospheric disturbances.
• Employs a CHSH Bell test to verify entanglement fidelity under dynamic and adverse environmental conditions.

Experimental results

Research questions

• RQ1 Can quantum entanglement be reliably distributed via drones under all-weather conditions?
• RQ2 What is the maximum distance and fidelity achievable for drone-based entanglement distribution with lightweight platforms?
• RQ3 How does symmetric beam aperture design and single-mode fiber coupling affect entanglement stability and visibility?
• RQ4 Can such a system be integrated into existing quantum networks, including satellites and fiber links?
• RQ5 What are the practical limitations of scalability and real-time operation in dynamic, outdoor environments?

Key findings

• The system achieved a CHSH S-parameter of 2.49, exceeding the classical limit of 2, confirming high-fidelity quantum entanglement under all-weather conditions.
• Entanglement distribution was successfully demonstrated over a 200-meter line-of-sight link in diverse weather conditions, including rain and fog.
• The entire drone system, including optical and control components, had a total take-off weight of less than 35 kg, enabling portability and scalability.
• The use of symmetric beam apertures and single-mode fiber coupling significantly improved signal stability and reduced mode mismatch.
• The system demonstrated robustness to atmospheric turbulence and mechanical vibrations during flight, maintaining consistent entanglement visibility.
• The platform is compatible with both local-area plug-and-play deployment and integration with high-altitude drones for wide-area quantum networking.