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Evaluation of the results of the latest research and development activities in the field of communication systems and in terms of their innovative capacity (continuation fifth articles)

2013-01-02
Andrew (Gabriel) Livshits

Fold in the current state of cyber warfare permanent forced as always in such cases, the search for an innovative solution to the situation
We offer our readers a summary of search and research in this area

Physicists at the University of Rochester have proposed a radar signal that can not be unnoticed intercept and forge. Preprint of the paper is laid out in the archives of Cornell University, and his summary of the results in a blog Technology Review.
Diagram of the proposed radar like the principle quantum key exchange. In the latter case, the quantum properties of photons are used to test the reliability of the information, which came from the source to the destination (which is usually denoted by Alice and Bob, respectively, and an attacker who tries to intercept their communications, called Eve).
Information that Alice sends to Bob, usually coded polarization of single photons or small groups. The reliability of such a transfer is that it is impossible to measure the state of a photon without destroying it, and therefore, any attempt to intercept this will be visible to Bob.
In the case of radar, Alice and Bob are the same person (transmitter and receiver radar beam), and Eve means a vehicle that is trying to capture the radar signal and modify it so as to change its apparent shape or location.
The authors showed that the tactics of the enemy can be opened, if used in radar technology transfer quantum key. In this case, in addition to the data itself (the form of the aircraft), Radar reported their level of reliability. Fake signal, so it is easy to distinguish the present.
Recently, another group of researchers carried out a quantum key exchange between the ground station and a moving aircraft with an infrared laser.

Engineers have developed a technology that allows you to transfer quantum keys over existing fiber optic cables loaded. Work accepted for publication in the journal Physics Review X, and its summary regurgitate NatureNews and BBC News.
Usually for the transmission of quantum keys using specially selected optical channels. This is due to the fact that the message is encoded in the key of polarization of individual photons. To measure it, requires the absence of noise from extraneous particles of light in the optical fiber.
The authors have shown that the application of a special filtration system, quantum communication can be carried out even on existing loaded optical channels.
Filtering technology is based on a calculation of the time it takes a photon to cover the distance from the transmitter to the receiver. Knowing when you should see a photon, can be identified by measuring its narrow time window and discard all particles that do not fit into it. However, according to the authors, the width of the window should be no more than 0.1 nanoseconds, which is ten times less than that required for the full measurement. To avoid this limitation, the researchers performed a single measurement in a narrow window, every nanosecond, and then by comparing the obviously empty and full boxes determines the polarization of the particles.
As a result, engineers have been able to establish a channel of delivery megabit quantum key length of 90 kilometers on the basis of an optical fiber, which received standard parallel data transfer.
Keys in cryptography called small messages used to decrypt large amounts of data. Quantum keys are fundamentally different from the usual topics that can not be intercepted by an attacker silently. This is prevented by the quantum nature of the media, because interception requires the measurement of a quantum state, and it is destroyed in the measurement. More on quantum cryptography can be found here and here.

Chinese Physics implement teleportation of photons at a record distance of 97 kilometers in the open air. The work of scientists is not accepted for publication, but its preprint available at Cornell.
Transmission of entangled photons was performed using a laser power of 1.3 watts over the lake, situated at the level of four thousand meters above sea level. Since the main problem in the transfer of that distance was the broadening of the beam physics have decided to use the optional laser guide, who helped arrange the receiver and transmitter. In addition to broadening the beam photon losses were caused by imperfect optics and air turbulence.
However, 4 hours managed to pass at a distance of 97 kilometers around 1100 of entangled photons. Scientists say that the observed losses are not too great and it is hoped that in the near future quantum teleportation of photons could be carried out between the ground station and satellite communication. The more so that the distance achieved by physicists, only a fraction of the typical distance between the satellite and the Earth.
Scientists conducted the transmission of entangled photons before, but until now it has been severely limited in range. Photon transmission over fiber could make for less than a kilometer, because the particles interact with the propagation medium (glass) and lose their quantum properties. Transfer by air was significantly more effective.
Many experts in data encryption hope that the technology transfer of entangled photons over long distances can be a basis for the establishment of channels of communication, virtually invulnerable for those wishing to intercept the transmitted message. Alternatively, the transmission of entangled photons, physicists consider the transfer of single photons, which will intercept immediately noticed the receiving end

German physicists have created a photon cannon, capable of emitting single photons of different wavelengths. Such devices may be essential for the organization of quantum communication, inaccessible to hackers. Preprint is available in the archives of the Cornell University.
Photon Cannon, developed by physicists, is a disc-shaped crystal of lithium niobate (compounds of lithium, niobium and oxygen), irradiated by the laser. Solid-state laser (like Nd: YAG) crystal pumped into photons with a wavelength of 532 nanometers. Photons flock reflected from the walls of the crystal, and can, because of its special properties, undergo decay into two photons with a similar, but slightly different wavelengths around 1060 nm.
Ultimately photons leave the crystal, which are divided into three groups. Initial particle wavelength of 532 nm are ignored, and a pair of long-wave separated. One of the photons is used for communication - sent to the receiving end. A second photon is a signal that the first ready to leave.
The need for communication of single photons is due to the problem of eavesdropping. The fact that all current existing lasers emit photons "bundles." If they are used for the transmission of information, the photons from the "pack" can be intercepted by an attacker in such a way that the receiving party will not notice. If the message is only one photon, it will go to the presence of an attacker eavesdropping and will be immediately detected.
In addition, since the formation of photons - a random process, it is necessary to use a pair of photons to by the presence of one of them to know that the second went to the transferee.
Authors were able to show that the heating or cooling the lithium niobate crystal, you can change the wavelength of the photons generated in the range of one hundred nanometers. Using a panel of such crystals can greatly increase the speed of transmission over a single channel.
Recently, physicists have created a quantum communication channel record length. Read more about how scientists are trying to adapt to the effects of quantum communication can be read here.

... to be continued ...

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