- Quantum photon source operates directly within existing telecom fiber wavelength ranges
- New quantum dots create identical single photons suitable for secure communication systems
- Support for silicon chips paves the way to a scalable quantum network
European researchers at the Niels Bohr Institute say they have solved a long-standing physical barrier that blocked quantum networks in traditional fiber systems.
Their work focuses on producing 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 activated by a laser pulse. That controlled emission allows quantum information to move across fiber lines without duplication, which is necessary for secure quantum communication systems.
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Overcome a noisy problem
Previous quantum dot designs produced reliable single photons, but they appeared at wavelengths around 930 nm that were inconsistent with telecommunications infrastructure.
Standard fiber networks operate at longer wavelengths, starting near 1260 nm, leaving researchers stuck with signals that have difficulty traveling useful distances outside of laboratory environments.
That mismatch was overcome by engineering quantum dots that directly emit photons around 1,300 nm, placing them within 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 remained one of the most persistent problems because it is necessary to produce identical photons 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 to be very challenging,” said Niels Bohr researcher Leonardo Midolo.
The tiny structures behind this breakthrough contain approximately 30,000 atoms and measure around 5.2 nm high and 20 nm wide, behaving like artificial atoms under laser stimulation.
Upon excitation, the trapped electron releases exactly one photon, producing a repeatable quantum signal suitable for communication and computing tasks.
Manufacturing these devices relies on highly controlled chip manufacturing techniques that shape materials into nanoscale photonic circuits.
“At the Niels Bohr Institute, we use advanced nanofabrication in our clean room to pattern these materials into quantum photonic circuits,” said Marcus Albrechtsen, joint first author of the study.
“We fabricated nanochips and tested them with lasers at low temperatures to confirm that they emit highly coherent single photons.”
Support for silicon photonic chips adds a huge practical advantage because silicon already dominates large-scale optical hardware manufacturing around the world.
Operating directly at telecom wavelengths allows these quantum emitters to be integrated into existing chip platforms without rebuilding entire production processes from scratch.
However, researchers still face major engineering challenges, as scaling laboratory prototypes to continent-spanning quantum networks requires reliable repeaters and long-distance signal handling hardware.
Still, the signs are good. “It opens up a lot of possibilities, possibilities that for a long time were considered out of reach,” Midolo said.
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