- Quantum photon source operates directly within existing telecommunication fiber wavelength ranges
- New quantum dots create identical single photons suitable for secure communication systems
- Compatibility with silicon chips opens the way towards scalable quantum networking
European researchers at the Niels Bohr Institute say they have solved a long-standing physics barrier that blocked quantum networks over traditional fiber systems.
Their work centers on producing perfectly controlled single photons that travel through the same optical cables already used across modern telecommunications networks.
The team created quantum dots that release exactly one photon at a time when triggered by a laser pulse. The controlled emission allows quantum information to travel through fiber lines without duplication, which is necessary for secure quantum communication systems.
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Overcoming a noisy problem
Previous quantum dot designs produced reliable single photons, but they appeared at wavelengths around 930nm that did not match the telecommunications infrastructure.
Standard fiber networks operate at longer wavelengths starting near 1260nm, leaving researchers stuck with signals that struggled to travel useful distances outside of laboratory environments.
That mismatch was overcome by engineering quantum dots that emit photons directly around 1300nm, placing them within the same wavelength band used in global fiber networks.
It removes the need for complex frequency conversion hardware that previously added noise and slowed development.
Noise remained one of the most stubborn problems because identical photons must be produced repeatedly without variation between emissions.
“Noisy in this context means that you could not generate one photon after another with the same properties. The photons must be completely identical, and it has proven to be extremely challenging to achieve this level of quantum coherence in the telecommunications band,” says Niels Bohr researcher Leonardo Midolo.
The tiny structures behind this advance contain about 30,000 atoms and measure about 5.2 nm high and 20 nm wide, and behave like artificial atoms under laser stimulation.
Upon excitation, the trapped electron releases exactly one photon, producing a repeatable quantum signal suitable for communication and computational tasks.
Fabrication of these devices depends on highly controlled chip fabrication techniques that shape materials into nanoscale photonic circuits.
“At the Niels Bohr Institute, we use such advanced nanofabrication in our cleanroom to pattern these materials into quantum photonic circuits,” said Marcus Albrechtsen, co-first author of the study.
“We fabricate nanochips and probe them with lasers at low temperatures to confirm that they emit highly coherent single photons.”
Compatibility with photonic silicon chips adds a major practical advantage because silicon already dominates large-scale optical hardware manufacturing worldwide.
By operating directly at telecommunications wavelengths, these quantum emitters can be integrated into existing chip platforms without rebuilding entire manufacturing pipelines from scratch.
However, researchers still face major technical challenges, as scaling laboratory prototypes into continent-spanning quantum networks requires reliable repeaters and long-distance signal handling hardware.
Still, the signs are good. “It opens up a lot of opportunities, opportunities that were long considered out of reach,” Midolo said.
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