The features of unmanned aerial vehicles (UAVs), such as strong manoeuvrability, small size, and light weight, make them considered to participate in free space optical (FSO) quantum communication, becoming an important part of the Space-Air-Ground Integrated Network. However, research reports on small-sized drones based long-range optical quantum link are few. A major challenge is that traditional opto-mechanical structure is difficult to adapt to small UAV platforms. Here, a lower size, weight, and power (SWaP) acquisition and tracking system prototype is developed, and its greatest advantage is that the system can be easily integrated into small flying platforms and quickly build a long-distance quantum communication link. The prototype weighs less than 8 kg. A small-sized two-axis mirror mechanism is designed for wide-range acquisition and tracking. Moreover, the system can automatically point to ground station. The SWaP acquisition and tracking system can support quantum key distribution (QKD) link and general FSO link by drones. In the 7 km air-to-ground demonstration, the acquisition and tracking system prototype is tested in practice, which is suspended under the small six-rotor UAV platform, and a special passive vibration isolation unit is added in between. A ten-minute continuous and stable beacon tracking proves that the system can quickly and automatically align.
The features of unmanned aerial vehicles (UAVs), such as strong manoeuvrability, small size, and light weight, make them considered to participate in free space optical (FSO) quantum communication, becoming an important part of the Space-Air-Ground Integrated Network. However, research reports on small-sized drones based long-range optical quantum link are few. A major challenge is that traditional opto-mechanical structure is difficult to adapt to small UAV platforms. Here, a lower size, weight, and power (SWaP) acquisition and tracking system prototype is developed, and its greatest advantage is that the system can be easily integrated into small flying platforms and quickly build a long-distance quantum communication link. The prototype weighs less than 8 kg. A small-sized two-axis mirror mechanism is designed for wide-range acquisition and tracking. Moreover, the system can automatically point to ground station. The SWaP acquisition and tracking system can support quantum key distribution (QKD) link and general FSO link by drones. In the 7 km air-to-ground demonstration, the acquisition and tracking system prototype is tested in practice, which is suspended under the small six-rotor UAV platform, and a special passive vibration isolation unit is added in between. A ten-minute continuous and stable beacon tracking proves that the system can quickly and automatically align.
The security of sensitive information exchange has become a major topic in recent years. Quantum Key Distribution (QKD) provides a highly secure approach to share random encryption keys between two communication terminals. In contrast with traditional public cryptography methods, QKD security relies on the foundations of quantum mechanics and not on computational capabilities. This makes QKD unconditionally secure (if properly implemented) and it is envisaged as a main component in the next–generation cryptographic technology. QKD has already been successfully demonstrated in different contexts such as fibre-to- fibre, and free-space ground-toground as well as ground-to-air communications. However, Size, Weight and Power (SWaP) constraints have prevented previous implementations to be demonstrated on small form airborne platforms such as Unmanned Aircraft Systems (UAS) and High Altitude Pseudo-Satellites (HAPS). Project Q-DOS aims to deliver a QKD module using compact, cutting-edge photonic waveguide technology, which will allow low-SWaP aerospace requirements to be met. This module uses 1550 nm single photons to implement a BB84 protocol, and will enable the demonstration of a secure, high-speed optical communication data link (~0.5 Gbps) between a drone and a ground station. The targeted link range is 1 km. The airborne communications module, including the QKD terminal, tracking modules, traditional communications systems, optics and control electronics, must not exceed a mass of 5 kg and a power consumption of 20 W.
Unmanned Aerial Vehicles (UAVs) are used in numerous applications ranging from defense, law enforcement, environmental monitoring, disaster recovery, aerial photography, and delivering consumer packages. Securing wireless communication between drones in-flight is critical to ensure safe operation during flight and avoid multiple types of attacks, e.g., eavesdropping, spoofing, jamming, etc. Quantum communication protocols offer enhancements over classical approaches. In this effort, we present progress towards demonstrating Quantum Key Distribution (QKD) between two drones in flight. A significant challenge includes achieving system performance using compact Size, Weight, and Power (SWaP) constraints of the drone vehicle. We introduce and evaluate critical subsystems including the QKD source, which is based on resonant-cavity Light Emitting Diodes (LED) controlled by an FPGA, and we discuss a secondary QKD source based on a fiber-coupled polarization modulator. The Pointing, Acquisition and Tracking (PAT) system is comprised of several cascading subsystems, which provide course alignment using based on Infrared (IR) beacons/cameras with gimbals, and fine alignment using Fast Steering Mirrors (FSM) with absolute encoders and feedback position sensors. We discuss both transmit and receive optics including custom designed 3D-printed optical benches. Finally, we introduce single-photon detectors, FPGA-based time-tagger, and a novel statistical post-processing synchronization algorithm. Establishing a quantum communications link between drones in-flight is an important prerequisite for future drone-based quantum applications such as entanglement distribution, distributed quantum sensing, and Quantum Positional Verification (QPV).
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.
This study introduces a novel free-space optical (FSO) communication system, designed for quantum key distribution (QKD) effective up to 2 kilometers and extendable to 10 kilometers. Suitable for terrestrial and unmanned aerial vehicle (UAV) applications, the system centers around an advanced Pointing, Acquisition, and Tracking (PAT) model, specifically tailored for the demands of free-space quantum key distribution (FSQKD) communication. The PAT system, with its dual coarse and fine-tracking capabilities, is crucial in establishing and sustaining robust, quantum-secured optical channels. The fine tracking module, in particular, achieves an impressive 0.11 milliradian accuracy and a swift 3.5 millisecond response time. Key to the system's performance is the optimization of beam wavelengths to minimize beam divergence and diffraction losses, essential for the stable operation of the QKD system. A detailed link budget analysis identifies specific losses: diffraction loss at 5dB for 2 kilometers, escalating to 18.4 dB at 10 kilometers, and receiver insertion losses, including optical, coupling, and wavefront losses, at 10.5 dB. The system's modular design enhances its adaptability for various QKD scenarios. This study gives a detailed approach towards practical, scalable quantum communication networks.
Here, we demonstrate a field-deployable free-space optical link for quantum key distribution (QKD) between a ground station and radio-controlled electric vehicle (RCEV). Compact and high-performance acquisition, pointing and tracking (APT) system is developed for small tracking error down to 3.8 μrad and average link loss of 16 dB. Such link is within the requirement of normal QKD system. With automatic acquisition and coarse tracking, the APT system can automatically establish the free-space optical link in 10 minutes. It is the first step towards mobile quantum secure communication network. Based on RCEV, the quantum optical link can be reconfigured at different link distances. This result greatly improves the flexibility of the link construction for the future QKD applications.
Remarkable achievements have been witnessed in free-space quantum key distribution (QKD), which acts as an available approach to extend the transmission range of quantum communications.The feasibility of transmitting qubits through the free-space channel with the aid of moving platforms like satellites, aircraft, unmanned aerial vehicles (UAVs) has been verified.In view of the limited working time and resource consumption of the satellite-based QKD and the last-mile challenges of connecting satellite nodes with terrestrial networks, the airborne QKD is expected to provide flexible and relay links for the large-scale integrated network.This paper reviews the recent significant progress of QKD based on aircraft or UAVs, highlights their critical techniques, and prospects the future of airborne quantum communications.