Une percée majeure vers l’internet quantique

Big breakthrough towards quantum internet

Researchers have taken a major step toward a super-secure quantum internet, by creating a rudimentary network for exchanging information by teleporting three times, they revealed in a study Wednesday.

The quantum internet – which should not see the light of day for ten years – will be a large-scale network that connects users via new applications and is “impossible to achieve with the classic web”, explains Ronald Hanson of Delft University (Netherlands), co-author of this work. Published in Nature.
Information will not be exchanged in the form of classical bits – 0 and 1 in the base of computing – but in the form of quantum bits (qubits).

These qubits exploit the laws of quantum physics, which govern the world on an extremely small scale. One such property is entanglement, also called entanglement, a strange phenomenon where two entangled particles behave identically regardless of their distance: as if they were bound together by an invisible thread, they shared the same state.

Thus the state of the entangled qubit is shared with the other, and the coordination between them is so perfect that one speaks of teleportation: in theory, any modification of the properties of one changes the properties of the other instantaneously, even at the other end of the Earth.

Quantum bits can currently be transmitted over optical fibers, but teleportation remains limited: after a hundred kilometers, the signal is weak or even missing. If we want to preserve end-to-end entanglement, the qubits must be directly related to a quantum “chain”.

This is the exploitation described in the study of nature, by which scientists have introduced a relay, in order to extend the range of communication. Quantum Communication, which was limited to two actors known as Alice and Bob, can now count on a third character, Charlie.

The experiment was conducted in two laboratories from QuTech, a collaboration between Delft University of Technology and the Dutch organization of applied sciences TNO.
Diamond-based qubits are enclosed in a circuit made up of three interconnections called ‘quantum nodes’. Alice and Bob’s nodes are located in two labs several meters apart, and are connected by fiber optics, similarly Bob is directly connected to Charlie. Alice and Charlie can’t talk to each other now.

The researchers first intertwined physically connected knots (Alice’s husband Bob and Bob’s husband Charlie). He then used Bob as a medium and, through the process of entanglement, was able to implicate Alice and Charlie.

Although they weren’t physically related, the last two were able to send a direct message to each other. The signal was also of excellent quality, without any loss – a challenge given the high instability of the qubit.

And this transmission was able to take place with the utmost secrecy, as required by the laws of quantum: with entanglement, any attempt to intercept or eavesdrop on the message automatically changes the qubits, destroying the message itself.

This first embryonic quantum teleportation network paves the way for large-scale connections: it demonstrates on a laboratory scale the principle of a reliable quantum repeater – the famous Bob – which can be placed between two nodes 100 kilometers apart, thus increasing the power. from the reference.

The innovation described in Nature represents a “victory for the basic sciences” and a “realistic solution to take applied quantum physics to the next level,” the scientists welcome in a “News & Views” commentary published on the sidelines of the study in Nature.

When talking about the quantum internet, physicist Ronald Hanson described a universe where communications would be “ultra-secure”, a quantum computer accessible in the cloud with “the privacy of our data guaranteed by +natural + laws of physics, a network of highly sensitive sensors…”.

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

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