The Kazan Quantum Center has tested 143 kilometers long fiber optic cables with quantum encryption. According to the developers, this achievement is a world record. The experiment was carried out on Rostelecom and Tattelekom networks.
Last year Rostelecom also tested the quantum communication line, but then its length was only 58 kilometers. The experiment was conducted on the networks of two telecom operators in Tatarstan. FOCLs continued from the Practical Quantum Cryptography Laboratory of KNITU-KAI to the Rostelecom communication center in Apastovo.
The Kazan Quantum Center was established in September 2014. Several laboratories, including the Laboratory of Quantum Memory and Communications, the Laboratory of Photonics and Fiber Quantum Optics, and the Laboratory of Practical Quantum Cryptography, are operating on its basis.
As for the cryptographic communication line, the participants of the experiment managed to solve the problem of transferring quantum keys over the fiber optic line at a long distance. For this purpose, the participants used a prototype of a data transmission and reception complex with hybrid quantum-classical protection. The complex, which is developed in KNITU-KAI, makes it possible to transmit quantum keys over long distances.
This complex includes a system of quantum distribution of keys at lateral frequencies, a crypt router and a highly efficient detector of single photons, which is produced by the Russian company "SCONTEL". The initial scheme of quantum distribution of the key was developed by specialists of the St. Petersburg National Research University of Information Technologies, Mechanics and Optics (ITMO University).
Optical losses during the testing of the cryptographic router were 37 dB. The participants of the experiment exchanged keys using a stream of single photons. They were recorded in quantum states of classical information.
According to the participants of the experiment, the frequency of modulation phase change was 100 MHz, the average number of photons per one cycle of modulation - 0.2. The 256-bit key was used during testing up to two times per minute. Such an opportunity was provided by the average speed of key generation in the channel.
Quantum encryption allows you to eliminate one of the main problems of modern encryption systems - the need to transfer the keys over the communication channel. They can be intercepted, after which the encryption loses its meaning - the data becomes available to third parties. As for quantum encryption systems, here in case of connection of the third party to a communication line the condition of single photons changes that does interception of the information impossible in current conditions.
There is also a disadvantage of this type of communication - the ease of changing the state of the photons, which makes it difficult to transmit information if the length of the channel exceeds 100 km. The transmission speed also leaves much to be desired.
Last February, the Chinese held a quantum video session between the Chinese Academy of Sciences in Beijing and the Austrian Academy of Sciences in Vienna. Thus, both sides received the key. Video calls were made through a traditional channel.
The first functioning quantum-cryptographic system was created in 1989 at the IBM Research Center by scientists Bennett and Brassar. The system was a quantum channel, which worked, on the one hand, with the transmitting apparatus of Alice, on the other - with the receiving apparatus of Bob. Both machines were 1 metre apart.
It was controlled by a computer, which was used to download software representations of the legal users of the attacker Eva, who was trying to "eavesdrop".