A breakthrough in the field of quantum communication
In modern information networks, data is transmitted in the form of a stream of flashes of light through an optical fiber: if there is a flash, one, if not, a zero. But such a transfer of information is unsafe, because these flashes can be quite easily “peeped” using a special technique, while neither the recipient nor the sender will be aware that the message was intercepted.
In the case of quantum communication, photons are transmitted in certain groups, and zeros and units are recorded in a special way. In the event that someone wants to intercept the letter, he will probably do it, but this, firstly, will not go unnoticed, and secondly, he is unlikely to read this message.
For the first time such an algorithm was invented by the American physicist Charles Bennett and Canadian cryptologist Gilles Brassard in 1984 year. Five years later, the algorithm was implemented in a laboratory - cryptophotons were transmitted through the air at a distance of thirty centimeters. However, with regard to industrial use, the first solutions appeared only in 2002-2004. But until now they are a very expensive pleasure, the cost of which is estimated at hundreds of thousands of dollars. It is impossible to eavesdrop on a quantum communication channel physically, since this is contrary to the laws of quantum mechanics.
At the same time, there is a big problem associated with the integration of quantum channels into a single network, since quantumness is violated in network nodes. Currently, the European Union has set about implementing a very ambitious global quantum network project called SECOQC, but in it cryptophotons will be converted into bits and transmitted through trusted network nodes. While quantum communication can be used only between two objects, and the distance between them should not exceed 200 kilometers, because for long distances single photons simply can not reach. Moreover, the greater the distance, the slower the data transfer rate, up to several hundred bits per second of time.
All existing installations using quantum communication are limited to the transfer of encryption keys, so very often quantum communication is called “quantum crypto”. After the objects receive the necessary keys, they encrypt the information and transmit it over the network. But at the same time, the keys for encryption should change very often, since the connection speed remains very slow.
The question arises: if there are so many problems with quantum communication, why not use open PGP-type cryptographic programs and do without quanta? The answer is simple: the fact is that despite all the convenience of public key systems, no one can guarantee their reliability. At the same time, among closed programs, there are those that cannot even be theoretically cracked, but all parties need to be provided with the necessary keys in advance, and this problem is almost impossible to solve in modern computer systems. But it can be solved with the help of quantum communication: the physicist helps to make sure that no one has intercepted the key, the physics helps, and the unavailability of the data encrypted with it is mathematics.
At the same time, it is worth mentioning that the concept of “unconditional security” is not entirely correct. Yes, powerful computer technology does not help to get to classified information, but there are other ways, for example, side channels of data leakage, technical errors, or “Trojan attacks”.
The enthusiasm of physicists was passed on to industrialists, businessmen, and government agencies. Young companies that have not yet been able to really sell the first quantum black boxes offer multimillion-dollar funding for further research. Very seriously, the ideas of quantum communication began to advance in the public consciousness. The first in this regard were the Swiss, who demonstrated the benefits of quantum communication during the parliamentary elections of the 2007 of the year. And although it really was a small benefit, but the PR turned out to be just great, because the Swiss population is very responsible about the electoral process. Therefore, the correctness of the counting of votes is important for them. And the connection of quantum communication and the protection of election results is a well-thought-out advertising move, which drew attention not only to quantum communication, but also to the development of Swiss science.
The development of quantum communication continues very intensively. And in May of this year, it was reported that Chinese physicists managed to transfer photons at a record distance equal to 97 kilometers through the open air. The transfer of entangled photons was carried out using a laser whose power was equal to 1,3 watts. The experiments were conducted over the lake, located at an altitude of 4 thousand meters above sea level. The main problem in the process of transmitting photons at such a significant distance was related to the beam broadening, so scientists used an additional guide laser, with which the receiver and transmitter were adjusted. In addition, photons were lost not only because of the broadening of the beam, but also because of the imperfection of the optics and the turbulence of the air.
Anyway, during the 4-hour experiment, we managed to transfer about 97 entangled photons to a distance of 1100 kilometers. But, according to scientists, the loss of photons is quite insignificant, so it can be assumed that in the near future, quantum communication can be made between a communication satellite and a ground station.
Note that scientists have previously conducted research on the transmission of entangled photons, but the transmission distance was not long - about a kilometer. The reason for this is the interaction of particles with the propagation medium, and, as a result, the loss of quantum properties. As you can see, the transmission by air proved to be more efficient.
A few days after the Chinese experiment, information appeared that European scientists managed to break the record of Chinese scientists, transferring entangled photons to a distance equal to 143 kilometers. According to its authors, the experiment lasted more than a year. The reason for this - bad weather conditions. It is known that the experiments were conducted in the Atlantic Ocean between the islands of Tenerife and La Palma. As in previous studies, the transfer of information was carried out in two channels - the usual and quantum.
It is now becoming apparent that the achievement of Chinese physicists proved more successful. Scientists for the first time managed to use a quantum connection between the base ground station and an airplane flying at a considerable height.
On board the Do228 aircraft flying at an altitude of 20 kilometers at a speed of 300 kilometers per hour, there was a receiver and a source (infrared laser) of photons. The base station used the optical system, in the structure of which was a system of mirrors with high-precision drives, to determine the direction and position of the aircraft. After all the coordinates of the aircraft, as well as the optical system of the receiver, were accurately determined, the station equipment could determine the polarization of photons and use this information to decipher the quantum data.
The communication session lasted approximately 10 minutes. However, not all transmitted information was encrypted using quantum cryptography. The quantum method transmitted only encryption keys, which changed after a certain number of kilobytes of information (about 10 Kbytes), which was transmitted by the usual method. The key transfer method used is called the quantum key distribution; it uses different polarization of photons to encode units and zeros.
It should also be noted that the frequency of errors during a session did not exceed 5 percent, which can be considered a great success in the field of quantum communication.
Thus, we can say that scientists have managed to come close to the creation of a satellite quantum communication system. At the same time, there is an assumption that the organization of such a connection will require even less effort, since weather conditions have a great influence on the earth's surface, but in the vertical direction they should not be so significant.
According to experts, if the experiments are completed successfully, quantum satellite communication can be used to organize a secure information network between the embassies of those states that already have this technology.
At the same time, there are a certain number of scientists who believe that along with the ability to provide powerful protection of the transmitted information, quantum communication is not able to solve a number of other equally important problems. So, according to Bart Prenel, a professor at the Catholic University in Leuven, there are the following problems. First, a sender using a quantum connection must be sure that there is a very specific recipient at the other end. Therefore, it is necessary to give a secret code to both parties. But if it is possible for small, well-designed and organized nodes, then quantum communication cannot be used for mass use. Secondly, quantum cryptography makes it impossible to sign documents. Thirdly, quantum cryptography cannot guarantee the protection of information that is already stored. Indeed, in modern information systems, the main thing is not to protect the information transmitted, but to protect the end nodes where this information will be stored.
Therefore, from the point of view of commercial use, quantum cryptography will not be viable for some time.
Materials used:
http://www.dailytechinfo.org/infotech/4016-vpervye-realizovana-kvantovaya-svyaz-mezhdu-letyaschim-samoletom-i-nazemnoy-stanciey.html
http://cybersecurity.ru/it/159210.html/
http://rus.ruvr.ru/2012_05_21/75468427/
http://ru.wikipedia.org/wiki/%CA%E2%E0%ED%F2%EE%E2%E0%FF_%E7%E0%EF%F3%F2%E0%ED%ED%EE%F1%F2%FC
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