Entanglement distribution has been accomplished using a flying drone, and this mobile platform can be generalized for multiple mobile nodes with optical relay among them. Here we develop the first optical relay to reshape the wave front of photons for their low diffraction loss in free-space transmission. Using two drones, where one distributes the entangled photons and the other serves as relay node, we achieve entanglement distribution with Clauser-Horne-Shimony-Holt S parameter of 2.59±0.11 at 1 km distance. Key components for entangled source, tracking, and relay are developed with high performance and are lightweight, constructing a scalable airborne system for multinode connectio and toward mobile quantum networks.
Entanglement distribution has been accomplished using a flying drone, and this mobile platform can be generalized for multiple mobile nodes with optical relay among them. Here we develop the first optical relay to reshape the wave front of photons for their low diffraction loss in free-space transmission. Using two drones, where one distributes the entangled photons and the other serves as relay node, we achieve entanglement distribution with Clauser-Horne-Shimony-Holt S parameter of 2.59±0.11 at 1 km distance. Key components for entangled source, tracking, and relay are developed with high performance and are lightweight, constructing a scalable airborne system for multinode connectio and toward mobile quantum networks.
Satellites have shown free-space quantum-communication ability; however, they are orbit-limited from full-time all-location coverage. Meanwhile, practical quantum networks require satellite constellations, which are complicated and expensive, whereas the airborne mobile quantum communication may be a practical alternative to offering full-time all-location multi-weather coverage in a cost-effective way. Here, we demonstrate the first mobile entanglement distribution based on drones, realizing multi-weather operation including daytime and rainy nights, with a Clauser-Horne-Shimony-Holt S-parameter measured to be 2.41 ± 0.14 and 2.49 ± 0.06, respectively. Such a system shows unparalleled mobility, flexibility and reconfigurability compared to the existing satellite and fiber-based quantum communication, and reveals its potential to establish a multinode quantum network, with a scalable design using symmetrical lens diameter and single-mode-fiber coupling. All key technologies have been developed to pack quantum nodes into lightweight mobile platforms for local-area coverage, and arouse further technical improvements to establish wide-area quantum networks with high-altitude mobile communication.
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.
The rapid advancement of quantum physical devices is transforming the quantum Internet from theory to practice. To achieve the envisioned full-time and all-location coverage, mobile quantum networks using drones have been proposed as a critical supplement to existing fiber and satellite quantum links, especially in scenarios where traditional optical links are unavailable. Although experiments in drone-based entanglement distribution have been successfully conducted, the field currently lacks a systematic network architecture and a dedicated protocol stack to integrate drone nodes and coordinate complex network functions efficiently. To address this gap, we propose a comprehensive design framework for drone-based quantum entanglement networks. First, we introduce a hierarchical architecture consisting of a quantum backbone relay network and quantum local area access networks. Second, for the local networks, we develop a clustering model based on the classical-quantum combinatorial metric to dynamically select and manage cluster heads. Third, we design a layered protocol stack that modularizes the end-to-end quantum information transmission process into well-defined functional layers. Subsequently, based on this architecture and protocol stack, we present the integrated design of a quantum drone node. Finally, we evaluate the designed network architecture. The results demonstrate that the proposed framework can significantly reduce the network overhead and improve the end-to-end entanglement distribution rate. Our work lays the foundation for the scalable development of mobile quantum networks.
Airborne mobile links can provide a practical and cost-effective way to establish multi-node connection structures in free space. Previously, drone-based mobile quantum links have been proposed and developed. Entanglement distribution has been demonstrated on such link with up to two mobile nodes in multi-weather condition, showing great potential in constructing practical quantum networks. Here, we present a further characterization of transmission properties of the mobile link. Using the established two-stage acquire, pointing and tracking system with scalable transceivers, we build a robust link between drone and ground separated 200 meters away. Ten-minute continuous transmission of optical signals is demonstrated in the drone-to-ground link, showing long-time stability of such mobile link.
Quantum networks between mobile platforms enable secure communication, distributed quantum sensors, and distributed quantum computing. As progress towards a future quantum internet continues, connecting mobile platforms (e.g., unmanned drones, smart vehicles, ships, and planes) to quantum networks remains a challenge. For instance, engineering constraints for real-world mobile platforms require low size, weight, and power (SWaP) for quantum systems. Additionally, single photons must be routed to platforms that are in motion and experience vibrations. In this effort, we discuss progress toward developing and demonstrating quantum communication links, including decoy-state quantum key distribution (QKD), between mobile drone and vehicle platforms in several configurations (drone-to-drone, drone-to-moving vehicle, and vehicle-to-vehicle). We will discuss and analyze critical subsystems including our decoy-state QKD source based on resonant cavity light emitting diodes (LED), compact optical system design, pointing, acquisition, and tracking (PAT) subsystem, single-photon detectors, field-programmable gate array-based time-tagger, and a novel time-synchronization algorithm. In addition, we present system performance including tracking performance under multiple conditions and mobile platform configurations.
Quantum key distribution is a well-established approach for sharing a classical key between two parties. In most cases, the parties are at fixed locations and use an optical fiber or free-space channel with fixed telescopes. To enable flexible and mobile quantum key distribution applications, we are developing a drone-based system. Here, the entire quantum transmitter and receiver system must have low size, weight, and power so that it can fly on medium-scale drones (Group 2, 21-55 lb gross takeoff weight). We will describe these key technologies and our current progress on achieving secure key exchange between drones.