- Quantum photon source operates directly within existing wavelength ranges of telecommunications fibers
- New quantum dots create identical single photons suitable for secure communications systems
- Compatibility with silicon chips paves the way for a scalable quantum network
European researchers at the Niels Bohr Institute say they have solved a long-standing physical obstacle that blocked quantum networking on traditional fiber systems.
Their job is to produce perfectly controlled single photons that travel through the same optical cables already used in modern telecommunications networks.
The team created quantum dots that release exactly one photon at a time when triggered by a laser pulse. This controlled emission allows quantum information to flow through fiber lines without duplication, which is necessary for secure quantum communications systems.
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Overcoming a noise problem
Previous quantum dot designs produced reliable single photons, but these appeared at wavelengths around 930 nm that did not match the telecommunications infrastructure.
Standard fiber networks operate at longer wavelengths, starting near 1,260 nm, leaving researchers stuck with signals that struggle to travel useful distances outside of laboratory environments.
This mismatch has been overcome by engineering quantum dots that emit photons directly around 1,300 nm, putting them in the same wavelength band used in global fiber networks.
This eliminates the need for complex frequency conversion hardware that previously added noise and slowed development.
Noise remains one of the most stubborn problems, because identical photons must be produced repeatedly without variation between emissions.
“Noisy in this context means that you cannot generate one photon after another with the same properties. The photons must be perfectly identical, and achieving this level of quantum coherence in the telecommunications band has proven extremely difficult,” said Niels Bohr researcher Leonardo Midolo.
The tiny structures behind this advance contain around 30,000 atoms and measure around 5.2 nm high and 20 nm wide, behaving like artificial atoms under laser stimulation.
After excitation, the trapped electron releases exactly one photon, producing a reproducible quantum signal suitable for communication and computing tasks.
Manufacturing these devices depends on highly controlled chip manufacturing techniques that shape materials into nanoscale photonic circuits.
“At the Niels Bohr Institute, we then use advanced nanofabrication in our clean room to pattern these materials into quantum photonic circuits,” said Marcus Albrechtsen, co-first author of the study.
“We fabricate nanochips and probe them with low-temperature lasers to confirm that they emit highly coherent single photons.”
Compatibility with silicon photonic chips adds a major practical advantage, as silicon already dominates large-scale optical hardware manufacturing around the world.
Operating directly at telecommunications wavelengths, these quantum transmitters can integrate into existing chip platforms without completely rebuilding production pipelines.
However, researchers still face big engineering challenges, as scaling laboratory prototypes into continent-wide quantum networks requires reliable repeaters and long-distance signal processing hardware.
Despite everything, the signs are good. “This opens up many possibilities, possibilities that have long been considered out of reach,” Midolo said.
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