Quantum Internet Milestone Achieved: 99% Fidelity Over 30 Kilometers for 17 Days on Fiber-Optic Network in Berlin

Researchers at Deutsche Telekom Innovation Laboratories (T-Labs) in Berlin, collaborating with quantum networking company Qunnect, have demonstrated a significant advancement toward the quantum internet by achieving sustained, high-fidelity transmission of entangled photons over 30 kilometers of commercial fiber-optic network for 17 days. The experiment, conducted at T-Labs’ quantum research lab, maintained 99% fidelity while automatically compensating for environmental changes and achieved only 1% network downtime.

Additionally, the system successfully coexisted with classical data traffic, distributing entangled photons over a combined 82 kilometers of fiber with fidelities above 92%. These results, presented at the OFC conference in San Francisco, highlight progress toward integrating quantum technologies into existing telecommunications infrastructure and enabling future applications such as ultra-secure communication, high-precision time synchronization, and advanced sensing.

Researchers at Deutsche Telekom Innovation Laboratories (T-Labs) and Qunnect conducted a field experiment demonstrating sustained high-fidelity transmission of entangled photons over 30 kilometers of commercially deployed fiber for 17 days, achieving 99% fidelity. The system automatically compensated for changing environmental conditions, maintaining stability and performance with only 1% network downtime. This marks a significant advancement in the practical implementation of quantum communication technologies.

Additionally, the experiment successfully integrated entangled photon transmission with classical data traffic, achieving fidelities above 92% over longer distances. This capability is crucial for leveraging existing fiber optic infrastructure to support both traditional and quantum communication systems simultaneously. The results highlight the potential for seamless integration of quantum networks into current telecommunications frameworks.

The findings underscore the importance of distributing entangled qubits with high fidelity for enabling advanced applications in the quantum internet, such as secure communication, distributed computing, and precision sensing. This work contributes to the broader goal of developing scalable and reliable quantum networks that can operate within real-world conditions.

Coexistence of Quantum and Classical Data Traffic Achieved

The experiment demonstrated the successful coexistence of quantum and classical data traffic over existing fiber optic infrastructure. Researchers integrated entangled photon transmission with classical communication systems, achieving fidelities above 92% over extended distances. This integration utilized distinct frequency bands—quantum signals in the O-band and classical traffic in the C-band—to ensure minimal interference while maximizing bandwidth utilization.

The ability to simultaneously support both quantum and classical data streams is a critical step toward practical implementation of hybrid networks. Such systems leverage existing telecommunications infrastructure, reducing deployment costs and accelerating the transition to scalable quantum communication technologies. This capability ensures that future quantum networks can operate alongside traditional systems without requiring entirely new infrastructure.

The distribution of high-fidelity qubits is fundamental to advancing the quantum internet, enabling secure communication and precision sensing. This experiment successfully transmitted entangled photons over 30 kilometers with 99% fidelity for 17 days, showcasing the potential for practical implementation in real-world conditions.

The ability to coexist with classical data streams represents a critical step toward practical hybrid networks. Such systems reduce deployment costs and accelerate the transition to scalable quantum communication technologies by operating alongside traditional systems without requiring entirely new infrastructure. The integration of quantum signals in the O-band with classical traffic in the C-band demonstrates strategic optimization of bandwidth utilization while maintaining signal integrity.

The collaboration between T-Labs and Qunnect focuses on advancing hardware solutions that enable seamless coexistence of quantum and classical data streams. For instance, Qunnect’s Gotham Rack system allows users to replicate quantum network protocols on commercial fiber optic networks, showcasing practical applications within real-world telecommunications frameworks.

This work underscores the potential for existing infrastructure to support emerging quantum technologies, facilitating a gradual transition toward more advanced and secure communication systems.