Physically Secured Communication Through Quantum Physics
Fraunhofer HHI develops QKD systems that bring physically secured communication from the lab into real-world networks – validated in government networks, over 680 km of fiber, and even in the air. As one of the few institutes worldwide, HHI covers the full development chain: from photonic chips and single-photon detectors to turnkey systems and security certification.
Our Technology
The HHI QKD system is based on the BB84 Decoy-State protocol and integrates into existing networks without infrastructure changes. All classical communication channels use standard TCP/IP – no dedicated synchronization channel, no parallel network required. The quantum channel can be optically rerouted in under one second, making it fully compatible with dynamic SDN and ROADM networks.
| Fiber & Free-Space Links | Seamless Network Integration |
| Ready for deployment in fiber and free-space networks – validated in real-world scenarios: government communications, Berlinale film distribution, 680 km backbone Berlin–Frankfurt. | Compatible with SDN and ROADM networks. Quantum channel optically reroutable in under one second – no parallel network, no additional synchronization channels required. |
| Standardized KMS Interface | BB84 Decoy-State Protocol |
| ETSI-compliant key interface (GS QKD 004) – interoperable with commercial encryption devices. Protection against store-now-decrypt-later attacks. | Security based on physical laws – not mathematical assumptions. Any eavesdropping attempt is physically detectable and leaves unavoidable traces. |
| Full System Chain from One Source | Photonic Integration (PIC) |
| The design process starts from the quantum entropy source (QRNG) through the transmission to single-photon detection and ends at the post-precessing – all key components developed in-house at HHI. | Transmitter and receiver modules on HHI-developed PolyBoard and InP platforms. Compact, cost-efficient components – the foundation for future plug-in-card-sized telecom modules. |
Video
Quantum Key Distribution at Fraunhofer HHI
In this video, Dr. Nino Walenta introduces quantum key distribution and its role in securing data in the age of quantum computing. He explains how Fraunhofer HHI contributes to the QuNET initiative by developing systems based on fundamental principles of quantum physics.
Milestones & Demonstrations
2026: Q-net-Q completed: 680 km QKD backbone Berlin–Frankfurt successfully validated
The Q-net-Q research project successfully demonstrated a hybrid QKD network infrastructure under real operational conditions – a 680 km long-distance connection from Fraunhofer HHI in Berlin via Erfurt to DE-CIX in Frankfurt am Main, complemented by a 150 km regional test network in Sundhausen. Multi-vendor validation with SDN control. Co-funded with €11.8 million by BMBF and the EU (ERDF).
2025: Air-to-ground free-space QKD: quantum key distribution between aircraft and ground station (QuNET Key Experiment #3)
Quantum channels were measured multiple times for the first time between a DLR research aircraft (Dornier 228) and the mobile ground station QuBUS, with QKD technologies tested in flight – without a dedicated clock channel, using an entanglement source on board. Conducted by DLR, MPL, FAU, Fraunhofer IOF and HHI between Oberpfaffenhofen and Erlangen.
2025: "Mini-EuroQCI": Seven-domain demonstration at ECOC 2025
7 independent network domains, 8 KMS technology providers and 9 QKD systems using diverse technologies (DV, CV, entanglement-based, fiber, simulated satellite link) were interconnected live. Demonstrated applications: quantum-secured video conferencing, VPN encryption and secure data backup.
2024: QuNET key experiment: multiple users communicating quantum-securely simultaneously for the first time
In Berlin, multiple users communicated quantum-securely at the same time for the first time – demonstrating the scalability of QKD networks for multi-user scenarios in real networks. Four HHI QKD nodes (Bundesdruckerei, Strausberg, T-Labs, HHI) in continuous operation with SDN monitoring.
2022: QuNET presents first system solutions for highly secure quantum communication
In QuNET-beta, complete system solutions for government and industrial applications were presented, and integration with European quantum network infrastructures (EuroQCI) was initiated.
2022: QKD-secured film distribution at the Berlinale
As part of the EU project OpenQKD, HHI together with Colt, ADVA and ID Quantique integrated a QKD link into the festival's film distribution – high-resolution premiere films were transmitted quantum-secured against piracy for the first time.
2021: First quantum-secured video conference between two federal authorities
As part of the QuNET initiative, the first tap-proof video conference between BMBF and BSI was conducted over fiber and free-space links using QKD keys – a nationwide milestone for quantum-secured government communication.
Press Releases
- Quantum communication in real-world applications: research consortium validates hybrid network architectures over 680 km (Mar. 2026)
- QuNET Key Experiment 3: Quantum channels tested in flight (Oct. 2025)
- Industry workshop of the QuNET initiative: highly secure communication through quantum physics (Jun. 2025)
- QKD in action: Fraunhofer HHI brings quantum communication into real-world infrastructures (2025)
- Important milestone on the road to quantum communication networks: second QuNET key experiment (Sep. 2024)
- BMBF initiative "QuNET" presents systems for highly secure quantum communication (2022)
- First quantum-secured video conference between two federal authorities (Aug. 2021)
- Venturing into quantum technology: Fraunhofer HHI joins BMBF-funded research project Q.Link.X (2018)