Quantum communication in action - description, features and interesting facts

Quantum physics offers an entirely new way of protecting information. Why is it needed, is it impossible to build a secure communication channel now? Of course, you can. But quantum computers have already been created, and at the moment when they become widespread everywhere, modern encryption algorithms will be useless, as these powerful computers can crack them in a fraction of a second. Quantum communication allows you to encrypt information using photons - elementary particles.

Such computers, having access to a quantum channel, will somehow change the present state of photons. And trying to get information will damage it. The speed of information transfer is, of course, lower, compared to other existing channels, for example, with telephone communication. But quantum communication provides a much greater level of secrecy. This, of course, is a very big plus. Especially in the modern world, when cybercrime is growing every day.

Quantum bond for "dummies"

Once pigeon mail was superseded by telegraph, in turn, the telegraph dislodged the radio. Of course, it is today, it has not gone anywhere, but other modern technologies have appeared. Just ten years ago, the Internet was not distributed as it was today and it was difficult to get access to it-it was necessary to go to Internet clubs, buy very expensive cards, etc. Today, without the Internet, we do not live an hour, and we are looking forward to it 5G.

But the next new communication standard will not solve the tasks that are facing the organization of data exchange via the Internet, receiving data from satellites from settlements on other planets, etc. All these data must be reliably protected. And it can be organized with the help of so-called quantum entanglement.

What is a quantum bond? For "dummies" explain this phenomenon as a connection of different quantum characteristics. It persists even when the particles are spaced from each other a great distance. Encrypted and transmitted with the help of quantum entanglement, the key will not provide any valuable information to attackers who attempt to intercept it. All that they receive is different numbers, since the state of the system, with external intervention, will be changed.

But it was not possible to create a world-wide data transmission system, because after a few tens of kilometers the signal faded. The satellite launched in 2016 will help to realize the scheme of quantum key transfer over distances of more than 7 thousand km.

The first successful attempts to use the new connection

The very first protocol of quantum cryptography was obtained in 1984. Today this technology is successfully used in the banking sector. Famous companies offer cryptosystems created by them.

The quantum communication line is carried out on a standard fiber optic cable. In Russia, the first protected channel was laid between the branches of Gazprombank in Novy Cheryomushki and the Cow Wall. The total length is 30.6 km, errors in the transfer of the key occur, but their percentage is minimal - only 5%.

China launched a quantum communication satellite

The world's first satellite of this kind was launched in China. The Long March-2D rocket was launched on August 16, 2016 from the cosmodrome Tszyu-Quan. A satellite weighing 600 kg will fly for 2 years on a sun-synchronous orbit, 310 km (or 500 km) high as part of the program "Quantum experiments on a cosmic scale". The period of circulation of the apparatus around the Earth is equal to one and a half hours.

The satellite of the quantum bond is called Micius, or "Mo-Tzu", in honor of the philosopher who lived in the 5th century AD. And, as is commonly believed, was the first to conduct optical experiments. Scientists are going to study the mechanism of quantum entanglement and conduct quantum teleportation between a satellite and a laboratory in Tibet.

The latter transfers the quantum state of the particle to a given distance. To implement this process, you need a pair of entangled (in other words, concatenated) particles that are at a distance from each other. According to quantum physics, they are able to capture information about the status of a partner, even being far apart. That is, it is possible to influence a particle that is in a distant cosmos, affecting its partner, who is nearby, in the laboratory.

The satellite will create two entangled photons and send them to Earth. If the experience is successful, it will mark the beginning of a new era. Dozens of such satellites can not only ensure the widespread dissemination of the quantum Internet, but also quantum communication in space for future settlements on Mars and on the Moon.

Why do we need such satellites

But why do we need a quantum communication satellite? Is not the existing conventional satellites enough? The fact is that these satellites will not replace conventional ones. The principle of quantum communication is the coding and protection of existing conventional data transmission channels. With its help, for example, security was already ensured during the 2007 parliamentary elections in Switzerland.

The non-profit research organization Battelle Memorial Institute, conducts information exchange between offices in the United States (Ohio State) and Ireland (Dublin) using quantum entanglement. Its principle is based on the behavior of photons - elementary particles of light. With their help, information is coded and sent to the addressee. Theoretically, even the most accurate attempt at intervention will leave a trace. The quantum key will change immediately, and the hacker attempting will receive a meaningless character set. Therefore, all data that will be transmitted through these communication channels can not be intercepted or copied.

The satellite will help scientists test the distribution of the key between ground stations and the satellite itself.

Quantum communication in China will be realized thanks to fiber optic cables, with a total length of 2 thousand km and connecting 4 cities from Shanghai to Beijing. A series of photons can not be transmitted infinitely, and the greater the distance between stations, the higher the chance that information will be damaged.

After passing some distance, the signal fades, and scientists, in order to maintain the correct transmission of information, need a way to update the signal after every 100 km. In cables, this is achieved by using tested nodes in which the key is analyzed, copied by new photons and goes on.

A bit of history

In 1984, Brassard J. of the University of Montreal and Bennett Ch. From IBM suggested that photons can be used in cryptography to obtain a protected fundamental channel. They proposed a simple scheme for quantum redistribution of encryption keys, which was called BB84.

This circuit uses a quantum channel, through which information between two users is transmitted in the form of polarized quantum states. An eavesdropper listening to them can try to measure these photons, but he can not do it, as stated above, without distorting them. In 1989, at the IBM Research Center, Brassard and Bennett created the world's first working quantum cryptographic system.

What is the quantum-optical cryptographic system (KOKS)

The basic characteristics of the COCS (error rate, data transfer rate, etc.) are determined by the parameters of the channel-forming elements that generate, transmit, and measure quantum states. Usually, the COCS consists of a receiving and transmitting parts that are connected by a transmission channel.

Sources of radiation are divided into 3 classes:

• Lasers;
• Microlasers;
• Light emitting diodes.

To transmit optical signals as a medium, use fiber-optic LEDs, combined in cables of different design.

The nature of the secrecy of quantum bonding

Passing from signals in which the transmitted information is encoded by pulses with thousands of photons, to the signals in which one pulse, on average, accounts for less than one, quantum laws come into play. It is the use of these laws with classical cryptography that makes it possible to achieve secrecy.

The Heisenberg uncertainty principle is used in quantum-cryptographic devices and thanks to it any attempts at change in the quantum system make changes to it, and the formation obtained as a result of such measurement is determined by the accepted party as false.

Does quantum cryptography give a 100% guarantee against hacking?

Theoretically gives, but technical solutions are not entirely reliable. Attackers began to use a laser beam, with which they blind the quantum detectors, after which they cease to respond to the quantum properties of photons. Sometimes multi-photon sources are used, and crackers can be able to skip one of them and measure the identical ones.