The Chinese satellite has successfully delivered to the earth station a pair of tangled photons. The associated particles traveled a record length of between 1,600 and 2,400 kilometers and were still tangled. The success of the researchers will contribute to the creation of the first quantum satellite network.
In August 2016 China sent into orbit and launched the world's first satellite for quantum telecom Micius. A crystal is placed on its board, which generates pairs of tangled photons. On June 16, an experiment was published in the journal Science that allowed pairs of interconnected photons from orbit to three ground stations, spaced about 1,200 kilometers apart. Depending on the position of the satellite, the particle pairs traveled from 1,600 to 2,400 kilometers. This is a great achievement considering that the record for such a transmission was only 100 kilometers.
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For such long distances, the preservation of quantum entanglement between photons is very difficult, because the environment can influence their interconnection. The troposphere is the lowest and most dense layer of the atmosphere, which normally should exert a strong influence on entangled particles. It turned out, however, that photons shipped with laser beams remained tangled, so the method used by Chinese scientists is by far the most efficient of all.
This will allow China to create the world's first quantum satellite network, but the system has yet to be refined. China plans to launch further satellites in the coming years, which would have even more powerful laser beams on its equipment, as the Micius satellite could deliver tangled photons only at night.
Quantum satellite achieves 'spooky action' at record distance
Last year, China also created a 100,000 km quantum quantum communication line, which will be connected to the satellite quantum network in the future. The new form of communication will be impossible to hack because any attempt to read confidential information will cause it to be destroyed irretrievably, and the sender of the message will know of an unsuccessful attempt to intercept it.
