Fraunhofer ISI and Saarland University Publish Quantum Repeaters Technology Roadmap Under SQuaD Project

Fraunhofer Institute for Systems and Innovation Research ISI has released a technology roadmap on quantum repeaters compiled with Saarland University as part of the Umbrella Project for Quantum Communication Germany (SQuaD). The study, titled “Quantum Repeaters – A Technology Roadmap,” draws on scientific literature, expert interviews, and a workshop with 22 participants from academia and industry. Quantum repeaters are positioned as a key enabler for transmitting quantum information and entanglement over long distances, supporting applications such as quantum-secure communication via quantum key distribution, distributed quantum computing, and networks of quantum sensors.

Hardware Platforms for Quantum Repeaters

Unlike classical signals, quantum information cannot be copied or amplified due to fundamental quantum mechanical principles. This constrains the range of existing quantum communication systems. Quantum repeaters address the limitation by enabling distributed entanglement across greater distances.

The roadmap documents intensive research across several hardware platforms. These include color centers in diamond, single trapped atoms and ions, warm and cold atomic ensembles, rare-earth-ion-doped crystals, and semiconductor quantum dots.

No single approach has emerged as dominant. Each platform presents distinct trade-offs in storage time, efficiency, scalability, and compatibility with existing infrastructure. Hybrid systems combining elements from different platforms are identified as a potentially important direction.

Key technical challenges remaining include improving efficiency and storage times, raising transmission rates, integrating devices into telecommunications infrastructure, achieving standardization, and enabling industrial scaling. Short-term progress is expected through additional demonstrations of individual components and network functions under initiatives coordinated by the Physikalisch-Technische Bundesanstalt (PTB) and the Bundesamt für Sicherheit in der Informationstechnik (BSI).

Pathways to Commercial Quantum Networks

The authors identify extension of quantum-secure communication range via quantum key distribution as the primary near-term application. Longer-term possibilities include interconnection of spatially separated quantum computers for distributed computing and the eventual establishment of broader quantum networks, along with high-precision quantum sensor networks.

Dr. Lukas Weymann of Fraunhofer ISI, lead author of the study, notes quantum repeaters could eventually fulfill a role analogous to classical repeaters in today’s telecommunication networks. They would operate on entirely different physical principles by providing access to distributed entanglement as a novel resource.

The roadmap anticipates quantum repeaters capable of transmitting quantum information with lower losses than direct connections over long distances could be demonstrated for the first time before 2035. This would represent a significant milestone. In the longer term, demonstrations involving networks of distant quantum computers or global-scale quantum networks are projected.

Weymann emphasizes a sustained period of diverse research and close cooperation among science, industry, and policymakers will be required to move from laboratory results to commercially usable systems. Progress can build on existing German and European quantum ecosystems and policy frameworks such as the High-Tech Agenda Germany. Related national efforts include the Quantenrepeater.Net (QR.N) consortium coordinated by Saarland University and earlier work under SQuaD.

Bottom Line

Fraunhofer ISI’s SQuaD roadmap charts parallel technology paths for quantum repeaters to enable scalable long-distance quantum networks.

Find out more here.

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