Quantum repeaters that can store multiplexed signals; provide heralded signals of entanglement; and operate at telecommunications wavelengths have been developed by two independent research teams. Their work could prove to be an important step towards the creation of a scalable quantum internet.

If it can be built, a quantum internet would allow calculations to be distributed between multiple quantum computers – allowing larger and more complex problems to be solved. A quantum internet would also provide secure communications because eavesdropping on the exchange of quantum information can be easily identified.

The backbone of such a quantum network would be quantum-mechanically entangled links between different network points, called nodes. However, creating entangled links over long distances at high data rates remains a challenge. A big problem is that quantum information becomes degraded as it is transmitted, and the rules of quantum mechanics do not allow signals to be amplified by conventional repeater nodes. The solution could be quantum repeaters, which can amplify quantum signals while still obeying quantum physics.

Now, two independent research groups — one at the Institute of Photonic Sciences (ICFO) in Spain and the other at the University of Science and Technology of China (USTC) – have shown how quantum memories (QM) offer a path towards practical quantum repeaters.

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