--- title: "Quantum Keys Travel 18 Kilometers Across Hybrid Air-and-Fiber Network" url: https://daily.dev/posts/quantum-keys-travel-18-kilometers-across-hybrid-air-and-fiber-network-siajl2xwo source_url: https://thequantuminsider.com/2026/08/26/quantum-keys-travel-18-kilometers-across-hybrid-air-and-fiber-network type: article source: "The Quantum Insider" published: 2026-08-26T12:30:20.773Z updated: 2026-08-26T12:30:44.653Z tags: ["security", "networking", "quantum-computing", "cryptography"] reading_time: 9 upvotes: 0 comments: 0 language: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # Quantum Keys Travel 18 Kilometers Across Hybrid Air-and-Fiber Network **[The Quantum Insider](https://daily.dev/sources/thequantuminsider)** · 9 min read · 0 upvotes · 0 comments ## Summary Researchers in Italy demonstrated quantum key distribution across an 18-kilometer free-space optical link connected to standard telecom fiber, using adaptive optics to counter atmospheric turbulence. The system generated secret keys at about 1,000 bits per second using superconducting detectors and 200 bits per second with room-temperature detectors, despite roughly 30 decibels of channel loss. The work used commercial BB84-protocol QKD equipment from ThinkQuantum and could inform future satellite and terrestrial quantum networks, including ESA's Eagle-1 and SAGA programs. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### What secret key rate did the 18-kilometer free-space to fiber QKD experiment in Italy achieve? The field trial achieved an average secret key rate near 1,000 bits per second using high-efficiency superconducting nanowire detectors, and about 200 bits per second with compact room-temperature indium gallium arsenide avalanche diode detectors. This occurred despite roughly 30 decibels of total channel loss across the 18-kilometer free-space link plus fiber segment, using commercial ThinkQuantum BB84 equipment at 1,565.50 nanometers. _Anyone tracking real-world QKD performance benchmarks can follow experimental results like this on daily.dev._ ### How does adaptive optics help connect free-space quantum links to fiber optic networks? Adaptive optics corrects atmospheric turbulence that distorts light before it enters a single-mode fiber, which is essential for coupling free-space quantum signals into fiber-based infrastructure. The Padua experiment used a 41-centimeter telescope, a Shack-Hartmann wavefront sensor, and a deformable mirror with 64 actuators, achieving about 12% coupling efficiency into the fiber after correction. _Engineers exploring hybrid optical network designs can keep up with adaptive optics research via daily.dev._ ### What limits the correction speed of adaptive optics systems used in free-space quantum key distribution? The experimental controller's correction bandwidth reached only about 10 hertz, well below its estimated theoretical maximum of roughly 24 hertz, due to communication delays, sensor noise, and use of a general-purpose computer rather than dedicated real-time hardware. Researchers suggest dedicated real-time controllers could push bandwidth above 100 hertz, enabling better performance under strong daytime turbulence. _Those evaluating adaptive optics hardware tradeoffs for optical links can find related research on daily.dev._ ## Similar posts on daily.dev - [Quantum key distribution enables secure communication via hybrid and mobile channels](https://daily.dev/posts/quantum-key-distribution-enables-secure-communication-via-hybrid-and-mobile-channels-2ts4dij6i) · Phys.org · 1 upvotes · 0 comments - [Scientists Send Secure Quantum Keys Over 62 Miles of Fiber—Without Trusted Devices](https://daily.dev/posts/scientists-send-secure-quantum-keys-over-62-miles-of-fiber-without-trusted-devices-x0fgu1nl6) · Singularity Hub · 0 upvotes · 0 comments - [Record-breaking quantum key distribution transmission distance achieved alongside classical channels](https://daily.dev/posts/record-breaking-quantum-key-distribution-transmission-distance-achieved-alongside-classical-channels-k6p0kkl4t) · Phys.org · 0 upvotes · 0 comments - [Large-scale quantum communication networks with integrated photonics](https://daily.dev/posts/large-scale-quantum-communication-networks-with-integrated-photonics-ellxuk3yq) · Nature · 0 upvotes · 0 comments - [Quantum key distribution method tested in urban infrastructure offers secure communications](https://daily.dev/posts/quantum-key-distribution-method-tested-in-urban-infrastructure-offers-secure-communications-dneh27qsh) · Phys.org · 0 upvotes · 0 comments --- Tags: [#security](https://daily.dev/tags/security), [#networking](https://daily.dev/tags/networking), [#quantum-computing](https://daily.dev/tags/quantum-computing), [#cryptography](https://daily.dev/tags/cryptography) [View this post on daily.dev](https://daily.dev/posts/quantum-keys-travel-18-kilometers-across-hybrid-air-and-fiber-network-siajl2xwo)