Scientists from QuTech (a collaboration between TU Delft and TNO) have connected quantum computers over a distance of 25 kilometers between Delft and The Hague, using regular internet fiber.

This connection between quantum computers is a step towards a quantum internet that transmits information as qubits.

This quantum internet could do things our current internet can’t, like making unbreakable codes for secure data sharing or connecting faraway quantum computers to work together, providing privacy and enhanced computing power.

“The distance over which we create quantum entanglement in this project, via 25 km of deployed underground fiber, is a record for quantum processors,” says research leader Ronald Hanson in a TU Delft press release. He adds that this is the first successful test to establish a quantum link quantum processors in different cities.

The scientists describe the methods and results of this project in a paper published in Science Advances.

Making this work outside the lab was challenging. The scientists had to ensure the persistence of quantum signals carried by photons, which is tricky over long distances. They used a method that was very precise in maintaining the stability of the light through the fiber.

“The link needed to be stable well within the wavelength of the photons (smaller than a micrometer) over 25 kilometer of optical fiber,” says researcher Arian Stolk. “That challenge compares to keeping the distance between the earth and the moon constant with the accuracy of only a few millimeter.” 

Toward a quantum internet for Europe

This project required a mix of academic knowledge and practical industry help. Various experts contributed, from developing frequency converters to providing the necessary fiber infrastructure. This collaboration shows how important partnerships between universities and companies are for advancing technology.

The success of this experiment lays a strong foundation for Europe’s quantum internet ambitions. It not only demonstrates the feasibility of quantum networking over metropolitan areas but also shows how current internet infrastructure can be adapted for quantum use. This work is a stepping stone towards a real quantum internet, potentially revolutionizing how we communicate and compute in the future.

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