Quantum physics offers a completely new way to protect information. Why is it needed, is it now impossible to lay a secure communication channel? Of course you can. But quantum computers have already been created , and at the moment when they become ubiquitous, modern encryption algorithms will be useless, since these powerful computers will be able to crack them in a split second. Quantum communication allows you to encrypt information using photons - elementary particles.
Such computers, having gained access to the quantum channel, will somehow change the present state of the photons. And an attempt to get information will lead to its damage. The speed of information transfer, of course, is lower in comparison with other currently 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 Communication for Dummies
Once the pigeon mail was replaced by a telegraph, in turn, the telegraph replaced the radio. Of course, today it hasn’t gone anywhere, but other modern technologies have appeared. Just ten years ago, the Internet was not spread as it is today and access to it was quite difficult - you had to go to Internet clubs, buy very expensive cards, etc. Today, we do not live an hour without the Internet, and we look forward to 5G.
But another new communication standard will not solve the problems that now face the organization of data exchange via the Internet, receiving data from satellites from settlements on other planets, etc. All this data must be reliably protected. And this can be organized with the help of the so-called quantum entanglement.
What is quantum communication? For "dummies" this phenomenon is explained as a connection of different quantum characteristics. It persists even when the particles are spaced apart from each other over a large distance. The key encrypted and transmitted using quantum entanglement will not provide any valuable information to crackers who try to intercept it. All they get are other 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, since after a few tens of kilometers the signal had faded. The satellite, launched in 2016, will help implement a quantum key transfer scheme for distances greater than 7 thousand km.
The first successful attempts to use the new connection
The very first quantum cryptography protocol was obtained in 1984. Today, this technology is successfully used in the banking sector. Well-known companies offer cryptosystems created by them.
A quantum communication line is carried out on a standard fiber optic cable. In Russia, the first secure channel was laid between the branches of Gazprombank in Novye Cheryomushki and Korovy Val. The total length is 30.6 km, errors occur during transmission of the key, but their percentage is minimal - only 5%.
China launched a quantum communications satellite
The world's first such satellite was launched in China. The Long March-2D rocket launched on August 16, 2016 from the Tszyu-Quan launch site. A satellite weighing 600 kg will fly for 2 years in a sun-synchronous orbit, with a height of 310 miles (or 500 km) under the program "Quantum experiments on a cosmic scale." The period of revolution of the apparatus around the Earth is one and a half hours.
The quantum communications satellite is called Micius, or "Mo-Tzu", in honor of the philosopher who lived in the 5th century AD. and, as is commonly believed, the first to conduct optical experiments. Scientists are going to study the mechanism of quantum entanglement and conduct quantum teleportation between the satellite and the laboratory in Tibet.
The latter transfers the quantum state of the particle at a given distance. To implement this process, you need a pair of entangled (in other words, entangled) particles located at a distance from each other. According to quantum physics, they are able to capture information about the state of a partner, even when they are far from each other. That is, it is possible to exert an effect on a particle that is in far space, acting on its partner, which is nearby, in the laboratory.
The satellite will create two entangled photons and send them to Earth. If the experiment is successful, it will mark the beginning of a new era. Dozens of such satellites can not only provide the ubiquitous spread of quantum Internet, but also quantum communications in space for future settlements on Mars and the Moon.
Why do we need such satellites
But why do we need a quantum communications satellite? Are existing conventional satellites not enough? The fact is that these satellites will not replace conventional ones. The principle of quantum communication is to encode and protect existing conventional data channels. With its help, for example, security was already ensured during the parliamentary elections in 2007 in Switzerland.
The non-profit research organization Battel Memorial Institute, is exchanging information between offices in the US (Ohio) and Ireland (Dublin) using quantum entanglement. Its principle is based on the behavior of photons - elementary particles of light. With their help, information is encoded and sent to the addressee. Theoretically, even the most accurate attempt at interference will leave a mark. The quantum key will change immediately, and the hacker who makes an attempt will receive a meaningless character set. Therefore, all the data that will be transmitted through these communication channels cannot be intercepted or copied.
The satellite will help scientists test the distribution of the key between the 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 uniting 4 cities from Shanghai to Beijing. A series of photons cannot be transmitted endlessly, and the greater the distance between the stations, the higher the chance that the information will be damaged.
After passing some distance, the signal decays, and scientists, in order to maintain the correct transmission of information, need a way to update the signal every 100 km. In cables, this is achieved with the help of proven nodes in which the key is analyzed, copied with new photons and goes on.
A bit of history
In 1984, Brassard J. of the University of Montreal and Bennett C. of IBM suggested that photons could be used in cryptography to provide a secure fundamental channel. They proposed a simple scheme of quantum redistribution of encryption keys, which was called BB84.
This scheme uses a quantum channel through which information between two users is transmitted in the form of polarized quantum states. An eavesdropping hacker may try to measure these photons, but he cannot do this, as mentioned above, without distorting them. In 1989, Brassard and Bennett created the world's first working quantum cryptographic system at the IBM Research Center.
What a quantum optical cryptographic system (COX) consists of
The main technical characteristics of the COX (error rate, data transfer rate, etc.) are determined by the parameters of the channel-forming elements that form, transmit and measure quantum states. Typically, the COX 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, fiber-optic LEDs are used as a medium, combined in cables of different designs.
The nature of the secrecy of quantum communication
Moving from signals in which the transmitted information is encoded by pulses with thousands of photons, to signals in which there are, on average, less than one per pulse, quantum laws come into play. It is the use of these laws with classical cryptography that allows secrecy to be achieved.
The Heisenberg uncertainty principle is applied in quantum cryptographic devices and thanks to it, any attempts to change the quantum system make changes to it, and the formation obtained as a result of such a measurement is determined by the accepted party as false.
Does quantum cryptography give a 100% guarantee against hacking?
Theoretically, but technical solutions are not entirely reliable. Attackers began to use a laser beam, with which they blind quantum detectors, after which they cease to respond to the quantum properties of photons. Multiphoton sources are sometimes used, and crackers may be able to skip one of them and measure identical ones.