Quantum Communications: Prospects

    (c) New quantum dot could make quantum communications possible The

    telegraph “killed” pigeon mail. The radio replaced the wired telegraph. Radio, of course, has not disappeared, but other data transfer technologies have appeared - wired and wireless. Generations of communication standards succeed very quickly: 10 years ago, mobile Internet was a luxury, and now we are waiting for 5G. In the near future we will need fundamentally new technologies that will be superior to modern technologies no less than wireless telegraphs - pigeons.

    What it can be and how it will affect all mobile communications - under the cut.

    Virtual reality, exchanging data in a smart city using the Internet of things, receiving information from satellites and from settlements located on other planets of the solar system, and protecting this entire stream - these tasks cannot be solved by the new communication standard alone.

    Quantum entanglement

    (c) New Experiment Allow Us To “See” Quantum Entanglement With The Naked Eye . In fact, we cannot see quantum entanglement, but beautiful visualization helps to understand the essence of the phenomenon.

    One of the main options for the evolution of communication awaiting us is the use of quantum effects. This technology does not exclude, but can complement the traditional forms of communication (although one cannot immediately reject the idea that a network based on quantum entanglement can theoretically supplant other types of communication).

    Quantum entanglement is a connection between quantum characteristics. The connection can be maintained even if the particles diverge over a large distance, since, by measuring the quantum characteristics of one of the bound particles, we automatically recognize the characteristics of the second as well. The first protocol of quantum cryptography appeared back in 1984. Since then, many experimental and commercial systems have been created based on the phenomena of the quantum world.

    (c) Chinese Academy of Sciences

    Today, quantum communication is used, for example, in the banking sector , where special security conditions are required. Companies Id Quantique , MAGIQ , the Smart the Quantumalready offer ready-made cryptosystems. Quantum technologies for security can be compared with nuclear weapons - this is almost an absolute defense, implying, however, serious implementation costs. If the encryption key is transmitted using quantum entanglement, its interception will not give attackers any valuable information - they will simply receive a different set of numbers at the output, because the state of the system into which the external observer intervenes changes.

    Until recently, it was not possible to create a perfect global encryption system - after a few tens of kilometers the transmitted signal died out. Many attempts have been made to increase this distance. China launched QSS ( Quantum experiments at Space Scale) satellite this year), which should implement the quantum key distribution scheme at a distance of more than 7000 kilometers.

    The satellite will generate two entangled photons and send to Earth. If everything goes well, then distributing the key using entangled particles will be the beginning of an era of quantum communication. Dozens of such satellites could become the basis not only of the new quantum Internet on Earth, but also of quantum communications in space: for future settlements on the Moon and Mars and for long-distance space communications with satellites traveling outside the solar system.

    Quantum teleportation

    Laboratory Key Quantum Distribution Device, Russian Quantum Center.

    In quantum teleportation, no material transfer of an object from point A to point B takes place - there is a transfer of "information", and not matter or energy. Teleportation is used for quantum communications, for example, for transmitting classified information. You must understand that this is not information in the form we are used to. Simplifying the model of quantum teleportation, we can say that it will allow us to generate a sequence of random numbers at both ends of the channel, that is, we can create a cipher block that cannot be intercepted. In the foreseeable future, this is the only thing that can be done with the help of quantum teleportation.

    The world's first photon teleportation took place in 1997. Two decades later, teleportation via fiber optic networks became possible for tens of kilometers (within the framework of the European program in the field of quantum cryptography, the record was 144 kilometers ). Theoretically, a quantum network can already be built in the city. However, there is a significant difference between laboratory and actual conditions. The fiber optic cable undergoes temperature extremes, due to which the refractive index changes. Due to the effect of the sun, the phase of the photon can shift, which in certain protocols will lead to an error.

    Kazan Quantum Center , laboratory of quantum cryptography.

    Experiments are conducted around the world, including in Russia. Appeared a few years agothe first quantum communication line in the country. She connected the two buildings of ITMO University in St. Petersburg. In 2016, scientists from the Kazan Quantum Center KNITU-KAI and ITMO University launched the country's first multi-node quantum network, achieving a speed of generating sifted quantum sequences of 117 kbit / s on a 2.5 km long line.

    This year, the first commercial communication line appeared - the Russian Quantum Center connected Gazprombank’s offices at a distance of 30 kilometers.

    In the fall, physicists at the Laboratory of Quantum Optical Technologies of Moscow State University and the Advanced Research Foundation tested an automatic quantum communication system at a distance of 32 kilometers, between Noginsk and Pavlovsky Posad.

    Given the pace of creating projects in the field of quantum computing and data transfer, in 5-10 years (according to physicists themselves), quantum communication technology will finally leave the laboratories and become as familiar as mobile communications.

    Possible disadvantages

    (c) Is Quantum Communication Possible

    In recent years, information security in the field of quantum communications has been increasingly discussed. It used to be that with the help of quantum cryptography it is possible to transmit information in such a way that it cannot be intercepted under any circumstances. It turned out that absolutely reliable systems do not exist: physicists from Sweden have demonstrated that under certain conditions quantum communication systems can be cracked due to some features in the preparation of a quantum cipher. In addition, physicists from the University of California proposed a method of weak quantum measurements, which actually violates the observer principle and allows one to calculate the state of a quantum system from indirect data.

    However, the presence of vulnerabilities is not a reason to abandon the very idea of ​​quantum communication. The race between attackers and developers (scientists) will continue at a fundamentally new level: using equipment with high computing power. Not every hacker can afford such equipment. In addition, quantum effects will probably speed up data transfer . Using entangled photons, almost twice as much information per unit time can be transmitted if they are additionally encoded using the direction of polarization.

    Quantum communication is not a panacea, but so far it remains one of the most promising directions for the development of global communications.

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