Deutsche Telekom & Qunnect Achieve 99% Quantum Fidelity
Researchers at Deutsche Telekom Innovation Laboratories (T-Labs), in collaboration with quantum networking hardware developer Qunnect, have achieved a significant breakthrough in quantum communications.
The two organisations successfully demonstrated high-fidelity transmission of entangled photons across 30 kilometres of commercially deployed fibre for 17 consecutive days.
The sustained 99% fidelity marks a crucial step towards realising a functional and scalable quantum internet using existing telecommunications infrastructure.
The trial took place in Berlin, using T-Labs' quantum research facility and fibre-optic network. T-Labs, Deutsche Telekom's R&D division, explores and advances disruptive technologies with strong business potential. Its work spans quantum networking, cybersecurity and digital twin solutions, often in collaboration with universities, startups and global technology partners.
Achieving stable, long-distance entanglement
Researchers distributed polarisation-entangled photons across a 30-kilometre fibre link in the primary field experiment. The system maintained performance over a 17-day period, with 99% fidelity and only 1% downtimeâsurpassing previous benchmarks in urban fibre networks.
Crucially, the system could compensate automatically for changes in environmental conditions, ensuring stability and reliability throughout the trial.
Further experimentation demonstrated the dynamic routing of entangled photons across multiple paths totalling 82 kilometres, while coexisting with conventional data traffic. Despite the added complexity, fidelities exceeded 92%.
The result represents the longest high-fidelity quantum entanglement distribution achieved in the O-band, multiplexed with classical data in the C-band, over commercial fibre infrastructure.
Noel Goddard, CEO of Qunnect, highlighted the importance of real-world integration, "We are grateful to T-Labs and Deutsche Telekom for the opportunity to showcase the performance of our products integrated with classical data traffic over commercial network infrastructure.
"Such partnerships are critical for demonstrating the progress towards commercial utility of quantum networking."
Quantum-compatible with existing infrastructure
The experiments leveraged Qunnect's advanced quantum networking hardware, including the Gotham Rack system, designed to facilitate entanglement distribution across real-world fibre optic networks.
The technologies were integrated into Deutsche Telekom's infrastructure without disrupting classical data trafficâhighlighting the compatibility of quantum and classical systems.
Claudia Nemat, Deutsche Telekom's Board Member for Technology and Innovation, stated: "Our fibre optics are ready for the Quantum Internet, even today.
"This is the first time that a major telecommunications provider has successfully triggered and conducted experiments with entangled photons on its own infrastructure.
"Our customers will benefit from such leaps in innovationâfor example, through highly secure communication."
Laying the foundation for the Quantum Internet
The ability to reliably transmit polarisation qubits over deployed fibre networks is essential for scaling quantum communications. These qubits are compatible with various quantum technologies, including quantum memories, sensors and computing devices, but they are notoriously difficult to stabilise in fibre environments.
The trial results strongly validate that existing telco networks can be the backbone for future quantum applications.
Quantum entanglement underpins more than secure communication. It enables services such as ultra-precise time synchronisation, which is essential for satellite systems and improved sensing for industrial IoT networks.
T-Labs sees the quantum internet not merely as a futuristic concept but as a technology capable of unlocking new services and efficiencies in the near term.
T-Labs' quantum research strategy
Since the opening of its dedicated Quantum Lab in Berlin in 2023, T-Labs has prioritised research into the application of quantum technologies in telecoms.
The lab connects to a national fibre network spanning more than 2,000 kilometres and collaborates with leading academic and industrial institutions, including technical universities in Berlin, Dresden and Munich, as well as the Fraunhofer Institute HHI.
T-Labs' research strategy focuses on seamlessly integrating quantum technologies to enhance network security and operational performance. Continued partnerships with companies like Qunnect are accelerating progress towards building commercially viable, secure and efficient quantum networks.
With this achievement, Deutsche Telekom and Qunnect have set a new benchmark for quantum communicationsâand signalled the beginning of a new era in European network infrastructure.
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