Quantum connection under the sea

This story initially appeared on ABA – Invest in Austria‘s website.

The quantum internet of the future should enable completely secure communication between users across the globe which is free from eavesdropping.

An international team of researchers from the Austrian Academy of Sciences and the University of Vienna established a quantum encrypted connection between Sicily and Malta via a submarine cable. The record distance of 192 kilometres was a further step in the development of a secure quantum internet. The team now reports on their experiment in the scientific journal “Nature Quantum Information”.
The researchers established a quantum-encrypted connection between Sicily and Malta via a conventional submarine telecommunications cable using entangled light particles. At the communication station on the coast of Malta, they first generated pairs of light particles that were entangled with each other via their random direction of oscillation, i.e. polarisation. The quantum key obtained in this way is secure: if an eavesdropper attempts to intercept such encrypted communication, the quantum physical state of the light particles would immediately change due to physical laws, and the “hacker” would immediately be caught.

This total distance of 192 kilometres is a new record for the method of producing quantum keys through polarisation-entangled light particles over longer distances on Earth. In this test setup, the transmission speed reached four bits per second.

The experiment at the bottom of the sea provided evidence of the unexpectedly high stability of the method and thus of the great potential it holds for the creation of a quantum internet of the future, by employing a conventional telecommunications infrastructure.

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