A major breakthrough towards quantum internet

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Paris (AFP) – Researchers have taken an important step towards an ultra-secure quantum internet by creating a rudimentary network for sharing information through three-way teleportation, they revealed in a study on Wednesday.

A quantum internet – which shouldn’t see the light of day for ten years – will be a large-scale network connecting users via new applications and “unachievable with the classical web,” explains Ronald Hanson of Delft University to AFP ( Netherlands), co-author of this paper published in the journal Nature.

The exchange of information does not take place there in the form of classic bits – the 0s and 1s as the basis of calculation – but in quantum bits (qubits).

These qubits use the laws of quantum physics, which govern the world on the infinitesimal scale. One of these properties is entanglement, also called entanglement, a strange phenomenon in which two entangled particles behave identically, regardless of the distance separating them: as if connected by an invisible thread, they share the same state.

The state of an entangled qubit is thus shared with the other, and their coordination is so perfect that it is called teleportation: in theory, any change in the properties of one instantly changes those of the other, even across the world.

Artist rendering provided by Delft University of Technology on May 25 depicting a quantum teleportation protocol using three diamond-based qubits Scixel TECHNICAL UNIVERSITY DELFT/AFP

Quantum bits can currently be transmitted over optical fibers, but teleportation remains limited: beyond a hundred kilometers the signal is attenuated or even lost. If we want to maintain end-to-end entanglement, the qubits must be directly connected by a quantum “chain”.

Alice, Bob and Charlie

This is the exploit described in Natural History, where the scientists introduced a relay to extend the range of communication. Quantum communication, which was limited to two actors commonly called Alice and Bob, can now count on a third figure, Charlie.

The experiment took place in two laboratories at QuTech, a collaboration between Delft University of Technology and the Dutch organization for applied sciences TNO.

Diamond-based qubits were placed on a circuit that included three connections dubbed the “quantum nodes.” The Alice and Bob nodes are in two labs several feet apart and connected by fiber optics, and similarly Bob is directly connected to Charlie. Alice and Charlie can’t talk to each other right now.

The researchers first entangled the physically connected nodes (the Alice-Bob pair and the Bob-Charlie pair). He then used Bob as an intermediary and through a process of entanglement exchange, managed to entangle Alice and Charlie.

Thus, although not physically connected, the latter two were able to message each other directly. The signal was also of excellent quality, with no losses – a challenge given the extreme instability of a quantum bit.

And this transmission could take place with the utmost secrecy, as required by quantum laws: with entanglement, any attempt to intercept or eavesdrop on the message automatically alters the qubits and destroys the message itself.

This first embryonic quantum teleportation network paves the way for large-scale connections: it proves on a laboratory scale the principle of a reliable quantum repeater – the famous Bob – which could be placed between two nodes further from 100 km away, thus increasing the strength of the signal .

The innovation, described in Nature, represents “a victory for basic research” and a “real solution to take applied quantum physics to the next level,” say scientists in a News & Views commentary published in Nature in the margins of the study .

Speaking about the quantum internet, physicist Ronald Hanson describes a universe where communication would be “ultra secure” and the quantum computer accessible in the cloud, where “the privacy of our data is governed by the + laws of nature + physics.” guaranteed”, a network of hypersensitive sensors…”.

Finding applications for the quantum network is “a research area in itself,” adds the researcher, who hopes this new world will be born “in less than 20 years”.

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