- Quantum photon source works directly inside existing telecom fiber wavelength ranges
- New quantum dots create identical single photons suitable for secure communication systems
- Compatibility with silicon chips opens path toward scalable quantum networking
European researchers at the Niels Bohr Institute say they have solved a long-standing physics barrier that blocked quantum networking 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. That controlled emission allows quantum information to move through fiber lines without duplication, which is required for secure quantum communication systems.
Overcoming a noisy problem
Earlier quantum dot designs produced reliable single photons, but those appeared at wavelengths around 930nm that did not match telecom infrastructure.
Standard fiber networks operate at longer wavelengths starting near 1260nm, leaving researchers stuck with signals that struggled to travel useful distances outside laboratory environments.
That mismatch was overcome by engineering quantum dots that emit photons directly around 1300nm, placing them inside the same wavelength band used in global fiber networks.
That 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 need to be produced repeatedly without variation between emissions.
“Noisy in this context means that you couldn’t generate one photon after another with the same properties. The photons need to be perfectly identical, and achieving this level of quantum coherence in the telecom band has proven extremely challenging,” said Niels Bohr researcher Leonardo Midolo.
The tiny structures behind this advance contain roughly 30,000 atoms and measure about 5.2nm tall and 20nm wide, behaving like artificial atoms under laser stimulation.
After excitation, the trapped electron releases exactly one photon, producing a repeatable quantum signal suited for communication and computation tasks.
Fabrication of 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 cleanroom to pattern these materials into quantum photonic circuits,” said Marcus Albrechtsen, joint first author of the study.
“We fabricate nanochips and probe them with lasers at low temperatures to confirm they emit highly coherent single photons.”
Compatibility with silicon photonic chips adds a big practical advantage because silicon already dominates large-scale optical hardware manufacturing worldwide.
Operating directly at telecom wavelengths allows these quantum emitters to integrate into existing chip platforms without rebuilding entire production pipelines from scratch.
Researchers still face big engineering challenges however, as scaling laboratory prototypes into continent-spanning quantum networks requires reliable repeaters and long-distance signal handling hardware.
Even so, the signs are good. “It opens up a lot of possibilities, possibilities that were long considered out of reach,” said Midolo.
