In this experiment, a semiconductor quantum dot serves as a source of polarization-entangled photon pairs at 780 nm. One photon was converted to telecom wavelength using a polarization-preserving frequency converter. Then it was transmitted within an intra-city fiber network across the city Stuttgart, preserving a high degree of entanglement. The study also showed that entangled photons could be converted to 1515 nm and back to 780 nm while maintaining their entanglement quality.

The research team used two cryostats to operate detectors at both NIR and telecom wavelengths, synchronized via a time tagger. The high efficiency, low noise, and precise time resolution of Single Quantum Eos were essential to the experiment’s success.

<< Working with Single Quantum systems has a big advantage: not only you operate with a state-of-the-art device, very much user friendly, but you can count on the persistent support of a team of highly trained professionals. >> Thank you, Dr. Simone Luca Portalupi, for your kind words!

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Institutions involved: Institut für Halbleiteroptik und Funktionelle Grenzflächen (University of Stuttgart), Fachrichtung Physik (Universität des Saarlandes), Leibniz IFW Dresden, and Deutsche Telekom T-Labs.