Drones Establish Secure Quantum Link over 1.2 Kilometres

A key advance in practical quantum communication networks has been achieved with quantum key distribution (QKD) now established between drones and ground stations. Chun Zhou and colleagues at the Key Laboratory of Quantum Information and Cryptography, in a collaboration between institutions in Zhengzhou, Hefei, and Anhui Asky Quantum Technology, have developed adaptive correction technology to enable a stable quantum link on a dynamic platform. The demonstration culminates in the first kilometer-scale drone-based QKD network, achieving a secure key rate of 2.76 kbps over 1.2km of free space, and 70.94 kbps over 100m with a relative speed of 1m/s. This achievement moves drone-based QKD from static laboratory tests towards the realisation of a truly airborne quantum internet with potential for urban deployment. Dynamic drone platform achieves record secure quantum key rate over 100 metres A secure key rate of 70.94 kbps now exists between a dynamic drone and ground vehicle over 100m, establishing a new benchmark for mobile quantum communication. Previously, mobile systems were limited to 2.76 kbps over 1.2km in static tests. This rate surpasses the threshold needed for practical, real-time applications, which were previously hampered by atmospheric turbulence and the challenges of maintaining a stable quantum link on a moving platform. The significance of exceeding this threshold lies in enabling applications requiring continuous, secure communication, such as real-time encrypted video conferencing or secure control of remote devices. Prior attempts at mobile QKD suffered from signal degradation due to atmospheric effects like scintillation, beam wander, and angle-of-arrival fluctuations, all of which introduce errors in the quantum signal and reduce the achievable key rate. These effects are particularly pronounced in free-space optical communication, where the signal travels through the unshielded atmosphere. The system utilises polarization adaptive correction technology, functioning like a self-adjusting telescope to counteract vibrations and atmospheric distortions, enabling the first kilometer-scale, dynamic drone-based Quantum Key Distribution (QKD) network. Drone-based QKD now advances from static demonstrations to practical dynamic networks, offering potential for an airborne quantum internet. The system employs a 1550nm laser and continuous polarization encoding, utilising a local oscillator scheme with heterodyne detection to reduce background noise during daylight operation. The choice of 1550nm wavelength is advantageous due to its relatively low atmospheric absorption and availability of suitable laser sources and detectors. Continuous polarization encoding, as opposed to discrete encoding, offers increased robustness against polarization drift, a significant challenge in free-space QKD. Heterodyne detection, by mixing the received signal with a local oscillator, improves the signal-to-noise ratio and allows for operation in bright daylight conditions, a crucial requirement for practical deployment. The local oscillator also aids in mitigating the effects of background radiation. A secure key rate averaging 70.94 kbps was attained between the drone and a ground vehicle 100m apart, alongside 2.76 kbps over 1.2km, validating performance in dynamic, three-dimensional scenarios. Precise positioning data from the BeiDou Navigation System, coupled with a dual-beacon structure and centroid algorithm, enables rapid acquisition and tracking with coarse tracking accuracy of 323 μrad and fine tracking accuracy of 38 μrad. Vibration isolation technology and a high-precision inertial navigation unit further stabilise the link, though these figures represent performance within a controlled 100m radius. The BeiDou Navigation System provides the necessary geolocation data for initial alignment and coarse tracking. The dual-beacon structure, employing two reference beams, allows for accurate determination of the drone’s position and orientation. The centroid algorithm then refines this tracking, achieving the stated accuracies. The inertial navigation unit compensates for short-term vibrations and accelerations, ensuring the quantum link remains aligned despite the drone’s movement. Sustained key rates over extended distances or in complex, densely populated urban environments remain to be seen, and the implications of this performance in more challenging conditions require further investigation. Demonstrating airborne quantum key distribution towards practical network deployment Free-space optics, transmitting data through the air using light, is gaining traction as a viable alternative to traditional fibre optic cables, particularly for connecting mobile devices. Maintaining a stable quantum link, essential for unhackable encryption, remains a considerable hurdle, as atmospheric turbulence and drone vibrations severely disrupt delicate quantum signals. Experts acknowledge that while adaptive correction technology mitigates these issues, scaling this network beyond its initial configuration presents a key challenge. The inherent fragility of quantum states means that any disturbance to the photons carrying the quantum information can introduce errors, compromising the security of the key exchange. This is why precise control over the optical path and robust error correction techniques are paramount. This demonstration of a kilometer-scale free-space quantum key distribution network, utilising drones, establishes a functioning mobile quantum communication system and moves the field beyond static laboratory tests. Secure key exchange between a drone and a ground vehicle at one metre per second opens questions regarding the scalability of this dynamic network architecture in complex urban environments, with future work focused on extending the range and durability of the system. The potential applications of such a network are diverse, ranging from secure communication for emergency services and critical infrastructure to providing secure links for mobile users in areas where fibre optic infrastructure is unavailable or impractical. Although achieving key rates of just a few kilobits per second may seem modest given current encryption standards, this demonstration represents an important step towards a practical airborne quantum internet. Current encryption standards often rely on computational complexity, which is vulnerable to advances in computing power, particularly the development of quantum computers. QKD, based on the laws of physics, offers information-theoretic security, meaning it is immune to attacks from even the most powerful computers. Further research will focus on increasing the key rate, extending the range, and improving the robustness of the system in adverse weather conditions and complex urban environments. This includes exploring advanced adaptive optics techniques, improved vibration isolation systems, and more sophisticated error correction codes.

This research successfully demonstrated a 1.2 kilometre quantum key distribution network using drones, achieving a secure key rate of 2.76 kbps. It matters because this establishes a functioning mobile quantum communication system, offering potentially unhackable data transmission based on the laws of physics rather than computational complexity. The ability to exchange keys between a drone and ground vehicle moving at 1m/s suggests the possibility of secure communication in areas lacking fibre optic cables or for mobile users. Future work will likely concentrate on increasing the key rate and extending the range of this airborne quantum internet, alongside improving system robustness in challenging conditions. 👉 More information🗞 Long Distance Daylight Drone-based Quantum Key Distribution under Relative Motion🧠 ArXiv: https://arxiv.org/abs/2603.18934 Tags: