Quantum Internet Is One Step Closer to Reality

Quantum Internet Is One Step Closer to Reality

Research Triangle Park, N.C. - US Army research results bring quantum internet a step closer. Such an internet could offer military security, detection and timing, impossible with traditional network approaches.

US Army Research Center for Combat Abilities The Center for Distributed Quantum Information, funded and managed by the Army Research Office, saw scientists from the University of Innsbruck achieved a record of quantum transfer of entanglement between matter and light - a distance of 50 kilometers using fiber optic cables.

Entanglement is a correlation that you can create between quantum units, such as qubits. When two qubits are entangled and a measurement is made on one, it will affect the measurement on the other, even if the other qubit is physically far away.

"This [50 kilometers] is two orders of magnitude farther than previously possible and is a practical distance to start construction of intercity quantum networks," said Dr. Ben Lanyon, experimental physicist at the University of Innsbruck and the main project researcher, whose results were published in the journal Nature Quantum Information (see link below).

Intercity quantum networks would be composed of distant network nodes of physical qubits, which are, despite the large physical separation, nevertheless entangled. This distribution of entanglement is essential for establishing a quantum internet, researchers said.

The demonstration is a major step forward for achieving large scale distributed entanglement,” said Dr. Sara Gamble, co-manager of the Army program supporting the research. “The quality of the entanglement after traveling through fiber is also high enough at the other end to meet some of the requirements for some of the most difficult quantum networking applications.

The research team started the experiment with a calcium atom trapped in an ion trap. Using laser beams, the researchers wrote a quantum state onto the ion and simultaneously excited it to emit a photon in which quantum information is stored. As a result, the quantum states of the atom and the light particle were entangled."The photon emitted by the calcium ion has a wavelength of 854 nanometers and is quickly absorbed by the optical fiber," said Lanyon.

Therefore, his team initially sent a light particle through a non-linear crystal illuminated by a strong laser. The photon wavelength has been converted to the optimal value for long distance travel - the current standard telecommunications wavelength of 1550 nanometers.

Then the scientists sent this photon through a 50 km long fiber line. Their measurements show that the molecules of the atom and light were still entangled even after converting the wavelength and distance traveled.

"Choosing the use of calcium means that these results also provide a direct path to the implementation of a tangled atomic clock network over a large physical distance, because calcium can be trapped with high-quality" clock "qubit. Large-scale networks of entangled clocks are very interesting for the army in terms of precise positioning, navigation and timing, "said Dr. Fredrik Fatemi, an army researcher who also manages the program.

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