Researchers from the University of Science and Technology of China and Jinan Institute of Quantum Technology
In their experiment, Bao and colleagues placedtwo quantum memory modules (a set of atoms) in different places in the urban environment, placing them at a distance of 12.5 km from each other. Scientists have created quantum entanglement by exciting a single atom at the first node. The photon emitted by the atom was transmitted along a 20.5 km optical fiber to another memory module, and connected the two nodes.
The researchers note that the photon emittedmemory module is in the near infrared (795 nm). This frequency is not suitable for low-loss fiber transmission. Therefore, the authors of the work used the quantum frequency conversion method to increase the photon wavelength to 1342 nm. After the signal arrives at the second module, the inverse transformation is carried out. This technology, as the creators believe, increases the quality of data transmission.
Although some previous researchshowed quantum communications over long distances, they mainly concerned the transmission of entangled photons or linked laboratories in the same building with a long fiber, the authors of the publication explain. In their work, the scientists linked quantum memory devices based on atoms separated by a large distance.
The quantum internet could open up bigopportunities for numerous applications of quantum technologies. For example, it could enable more secure communications, more accurate remote sensing, and distributed networks of quantum computing. However, to create them, many interconnected remote modules are required. The new work is a step towards building such networks, the physicists add.
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