• Deutsche Telekom’s T-Labs has been trialling quantum networking architectures
• T-Labs has completed a successful trial with specialist vendor Qunnect
• The partners enabled quantum connections over commercial fibre lines over 30km for 17 days

Deutsche Telekom’s Innovation Laboratories (T-Labs), in partnership with US/Dutch specialist vendor Qunnect, claims to have enabled sustained quantum networking (or quantum internet) connectivity with 99% fidelity for a period of 17 days over a 30km stretch of commercially deployed fibre in Berlin. The telco claims the trial’s success “represents a decisive step on the way to the quantum internet and demonstrates how existing telecommunications infrastructure can support the quantum technologies of tomorrow”.

Even though quantum computers are still at relatively early stages of development and at least 10 years from being widely commercially available, the race is on to enable next-generation quantum devices to be interconnected and able to exchange information and share entanglement, potentially enabling secure communications and advanced quantum computing capabilities – and the hope is that they will be connected over commercial fibre networks rather than require new, dedicated fibre infrastructure.

Slowly but surely, progress is being made in enabling quantum networking – indeed, news of DT’s trial was announced only days after two UK universities unveiled their own successful tests over an even longer distance of 410km – see UK claims major quantum comms network breakthrough.

One of the main challenges with quantum computers is that they are very sensitive to changing conditions, even as standalone devices, let alone in a networked environment.  According to DT, the trial quantum computing setup “automatically compensated to changing environmental conditions in the network, maintaining 99% fidelity. This performance was sustained for over 17 days with only 1% network downtime, surpassing previous demonstrations in metropolitan networks.” 

The trial’s success is notable because of the stability achieved over regular commercial fibre lines. As DT explains: “For the quantum internet to support applications beyond point-to-point secure networking, it is necessary to distribute the types of entangled photons, or qubits, that are used by quantum computers, sensors or memories. Polarisation qubits, like the ones used for this work, are highly compatible with numerous quantum devices, but they are difficult to stabilise in fibres. This success represents a decisive step on the way to the quantum internet and demonstrates how existing telecommunications infrastructure can support the quantum technologies of tomorrow.”

Claudia Nemat, a member of the board of management for technology and innovation at Deutsche Telekom, commented: “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 innovation, for example, through highly secure communication.”

Noel Goddard, CEO of Qunnect, added: “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.”   

And in a separate trial, “polarisation-entangled photons were dynamically routed over multiple paths, totaling 82kms in length, while coexisting with classical data traffic,” according to DT. “Researchers demonstrated fidelities above 92%. This is the longest demonstration of high-fidelity entanglement distribution in the O-band [original band spectrum], multiplexed with C-band [conventional band spectrum] classical data, ever performed over commercially deployed optical fibers. The results are currently posted on arXiv.”

Deutsche Telekom opened its Quantum Lab, a research facility equipped with an infrastructure for quantum optical experiments, in Berlin in 2023. It is connected to a fibre-optic network of more than 2,000km that links multiple partners, such as the technical universities in Berlin, Dresden and Munich,,as well as the Fraunhofer Institute HHI, throughout Germany. 

To keep up to date with the latest quantum-safe networking developments, check out TelecomTV’s dedicated quantum technology page.

- Ray Le Maistre, Editorial Director, TelecomTV