New quantum repeaters could enable a scalable quantum

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+  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.

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.

 

+  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.

+  Both teams’ approaches use photon-pair sources, where one photon is stored in the QM and the other is used as a signal to herald (or confirm) the entanglement. Multiplexing, by means of storing several signals at once using different photon wavelengths, is performed via atomic frequency comb protocols. This means that the systems do not have to wait for a successful heralding event before generating the next entangled pair. Equally important is that the heralding photons are at telecoms wavelengths, making the systems compatible with existing telecoms networks and allowing entanglement to be created over long distances using optical fibres.

+ The ICFO system uses a QM that stores photons in millions of atoms all randomly placed inside a rare-earth doped crystal. The team uses a set of photons at different wavelengths. One at 606 nm for storage, one at 1436 nm (telecom wavelength) for signaling that entanglement is achieved. The QM can store the signals for up to 25 µs, before releasing the signals. Entanglement is achieved between two QMs by storing a single photon in a superposition over the two QMs placed in different labs 10 m apart.

Source:  physicsworld.  Martijn Boerkamp,  New quantum repeaters could enable a scalable quantum…

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