China creates a quantum communication system from space, impossible to spy on | Science


THE China has just shown its technological power with a milestone that has great geostrategic implications: the pulverization of the quantum communication distance record. A team of scientists from the Asian country announced on Monday the first simultaneous transmission of a message encrypted with quantum technology, sent from a space satellite to two terrestrial telescopes separated by 1,120 kilometers, a distance about ten times greater than that reached until So.

Quantum phenomena originate on microscopic scales, but can have significant effects on the visible world. Two particles can be entangled in such a way that what happens to one happens to the other instantly, even if they are separated by billions of kilometers. If someone tries to observe these particles during their transmission, their state changes and the entanglement is broken. This property allows you to create a communication system theoretically impossible to breach or hack because mere observation by the spy destroys the message.

For years, China, Europe and the United States plan to develop quantum communication networks to send official messages or establish cyber security systems in strategic facilities.

In a study published today in Nature, Chinese scientists detail the transmission of a secret key written with pairs of photons “particles of light” intertwined. The photons are emitted by the Micius satellite, which orbits 500 kilometers from Earth, to two terrestrial installations built for this specific purpose in the cities of Delingha and Nanshan, separated by 1,120 kilometers. The use of a satellite is crucial, since the transmission of these messages using optical fiber loses many photons, in such a way that repeaters would be needed every approximately 100 or 150 kilometers. And a repeater, with all its mechanical components, can be hacked.

Each bit information is encoded using two interlaced photons. This time, the Chinese show the secure transmission of a secret 372-bit key. The key can be used to decipher an encrypted message that can be transmitted by any other means, including Internet and telephony.

In their work, Chinese researchers have tested their system against different types of attacks and have shown that it is safe. Speed ​​and efficiency are 100 billion times greater than terrestrial fiber. “Our work lays the foundations for a global network of quantum communication”, highlight those responsible for the study.

“Nobody was able to do this at such a great distance,” Juan José García-Ripoll, specialist in quantum communication at the Superior Council for Scientific Research (CSIC), Spain. “This is not a new protocol, but they have achieved something unique from a technical point of view. China is ahead in this field, ”he says.

The country has spent years investing large sums of money in new quantum communication technologies, both space and terrestrial. In the latter, he had already managed to connect Beijing and Shanghai with a fiber optic network for the transmission of quantum keys. In addition, China has achieved previous records in space communication, such as the transmission in 2017 of a quantum key that made it possible to maintain a non-hacked teleconference between Vienna and Beijing, more than 7,000 kilometers away, also using the Micius satellite.

“The difference is that, in this case, the satellite acted like a safe that holds the key while moving from point A to B and, during that period, is vulnerable to espionage”, explains Valerio Pruneri, a researcher at the Instituto de Photonic Sciences in Barcelona. Pruneri is the contact in Spain for the international network of European countries that has been shaping a major European Union project for just over a year to create a secure quantum communication network at a European level in a decade.

“This is still a scientific race, but it is increasingly clear that each continent needs to have its own network, it cannot depend on others to acquire it”, says Pruneri. The researcher recalls that the concept of quantum communication was coined in Europe, where the first fundamental experiments were carried out, but for years China has been strongly committed to mastering this technology. The head of the Chinese quantum communication system, Jian-Wei Pan, of the University of Science and Technology of China, graduated from the University of Austria in the late 1990s, and then returned to his country to begin the development of this technology.

“It is good news that China has achieved this because it shows technological viability”, says Pruneri. “This should put pressure on Europe to develop its own network with its own technology”, he observes.

The next major milestone would be the use of geostationary satellites, whose orbit about 35,000 kilometers from Earth would increase the distance that encrypted messages can be sent with quantum technology, something that Europe plans to do within the European Space Agency’s SAGA program.

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