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.
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.
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.
We present QuBUS, a mobile optical ground station designed for free-space optical communication (FSOC) and quantum key distribution (QKD). Built into a transportable lab container, QuBUS includes key subsystems such as an optical antenna with uplink lasers, a freeform telescope, acquisition and tracking hardware, relay optics, and an adaptive optics system for single-mode fiber coupling. The station is being prepared for an air-to-ground quantum communication experiment involving an aircraft-based transmitter. Initial 7-km horizontal link tests validate core functionalities, demonstrating QuBUS’s potential as a compact and deployable platform for future secure quantum communication networks.
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.
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.
Wireless quantum networking can provide flexible, rapidly deployable, and secure connectivity for mobile and infrastructure-limited scenarios. However, existing free-space continuous-variable quantum key distribution (CV-QKD) systems are still limited to point-to-point links, while dynamic multi-user access is hindered by bulky and slow mechanical beam steering. In this paper, we propose a free-space multi-user CV-QKD scheme based on an optical phased array. Based on a full-link model accounting for device imperfections and channel effects, numerical results demonstrate the feasibility of the proposed scheme under different atmospheric conditions and suggest its robustness and scalability. This work provides a promising route to rapidly reconfigurable free-space quantum access networks for highly dynamic near-range scenarios such as unmanned aerial vehicle swarms and emergency communications, and may inform future extensions toward satellite-based quantum networking.
This paper develops a comprehensive analytical framework for modeling and performance evaluation of unmanned aerial vehicles (UAVs)-to-ground quantum communication links, incorporating key physical impairments such as beam divergence, pointing errors at both transmitter and receiver, atmospheric attenuation, turbulence-induced fading, narrow field-of-view (FoV) filtering, and background photon noise. To overcome the limitations of conventional wide-beam assumptions, we introduce a grid-based approximation for photon capture probability that remains accurate under tightly focused beams. Analytical expressions are derived for the quantum key generation rate and quantum bit error rate (QBER), enabling fast and reliable system-level evaluation. Our results reveal that secure quantum key distribution (QKD) over UAV-based free-space optical (FSO) links requires beam waists below 10 cm and sub-milliradian tracking precision to achieve Mbps-level key rates and QBER below 10−3. Additionally, we highlight the critical role of receiver FoV in balancing background noise rejection and misalignment tolerance, and propose adaptive FoV tuning strategies under varying illumination and alignment conditions. The proposed framework provides a tractable and accurate tool for the design, optimization, and deployment of next-generation airborne quantum communication systems.