(Paris) Researchers have taken a key step toward an ultra-secure quantum Internet by creating a rudimentary network for exchanging information via triple teleportation, they revealed in a study on Wednesday.
A quantum internet – which should not see the light for another ten years – will be a large-scale network that will connect users through new applications and “impossible to achieve with the classic web”, Ronald Hanson explains to AFP, from the University of Delft (The Netherlands), co-author of this work published in the journal Nature.
The exchange of information will take place there not in the form of classical bits -the 0 and 1 at the basis of computing- but of quantum bits (qubits).
These qubits exploit the laws of quantum physics, which govern the world on the scale of the infinitesimally small. One of these properties is entanglement, also called entanglement, a strange phenomenon whereby two entangled particles behave identically no matter how far apart they are: as if linked 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 we speak of teleportation: in theory, any modification of the properties of one instantly modifies those of the other, even at the other end of the earth.
Currently, quantum bits can be transmitted through optical fibers, but teleportation is still 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 linked by a quantum “chain.”
Alice, Boba, and Charlie
This is the feat described in the study of Nature, through which scientists introduced a relay, to lengthen the communication range. Quantum communication, which was limited to two actors commonly called Alice and Bob, can now count on a third character, Charlie.
The experiment took place in two laboratories at QuTech, a collaboration between the Delft University of Technology and the Dutch applied science organization TNO.
The diamond-based qubits were placed in a circuit comprising three interconnections called “quantum nodes”. Alice and Bob’s nodes are located in two labs several meters 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 a go-between and through a process of exchanging entanglements, managed to entangle Alice and Charlie.
Although not physically connected, the latter two were able to send a message directly to each other. The signal was also of excellent quality, without any loss, a challenge gave the extreme instability of a quantum bit.
And this transmission could have taken place in the greatest secrecy, as required by quantum laws: with entanglement, any attempt to intercept or listen to the message automatically changes the qubits, destroying the message itself.
This first embryonic quantum teleportation network paves the way for large-scale connections: testing on a laboratory scale the principle of a reliable quantum repeater, the famous Bob, that could be placed between two nodes separated by 100 km, thus increasing the strength. Of the signal
The innovation described in Nature represents “a victory for basic science” and a “real-world solution to take applied quantum physics to the next level,” the scientists said in a “News & Views” comment posted on the sidelines of the study at Nature.
When he talks about the quantum Internet, the physicist Ronald Hanson describes a universe where communications would be “ultra-secure”, and the quantum computer accessible in the cloud with “privacy of our data guaranteed by the ‘natural’ laws of physics, a network of sensors hypersensitive…”
Finding applications for the quantum web is “a field of research in itself”, adds the researcher who hopes to see this new world born “in less than 20 years”.
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