In the laboratory, optical active media FIAN creates a unique quantum filter based on a rubidium atom.

The new quantum filter will convert the laser pulse into a single photon.

Installation has already been collected and is currently being conducted another series of experiments.
Obtaining controlled photon "on demand" method of filtering the laser pulse will be used in basic research. Such instruments will be needed, for example, for the development of quantum memory and create a fundamentally unbreakable encryption during data transmission.

The idea is to use the properties of the nuclear environment, organized in a certain way, for "filtering" with high probability, up to 100% of a single photon of the laser pulse. Offered her well-known theoretical physicists Valery Yudin and Alexei Taichenachev from the Novosibirsk State University.

If a four-level system (atom with four energy levels) to make a specially selected strong light field and the probe pulse, the pulse will be scattered in the environment for as long as it does not remain exactly one photon. But when the pulse will last a photon, the environment for it is now absolutely clear. There is transparency in this environment, when the frequency difference of the light fields coincides with the frequency difference of the two atomic levels.

The experimental setup was established in LPI includes two laser sources, some chains binding the cell with rubidium and a number of auxiliary devices. Says a senior researcher at the Laboratory of Optics of active media, the candidate of physical and mathematical sciences Alexei Akimov, "One creates a powerful laser field, the irradiated medium. The second — makes the light pulse, superimposed on it a lot of restrictions. Powerful field enlightens Wednesday and does not dissipate, it must be separated from the pulse — with the help of polarization interference filters. A number of devices can generate pulses and adjust their frequency to match the desired transitions in atoms of the medium. The required four-level state of rubidium atoms is supported by an external magnetic field. Gaseous Rb is 4-cm cuvette with a small vacuum by adding a buffer gas. "

Applications of the new device — fundamental research in quantum photonics, as well as work to create a quantum memory. After all, a single photon — this is the minimum quantum of information that can be transmitted at all. Related to this is another possible application — encryption when transmitting information. If you create a single photon in a specially-state, it can not be "measured", without spoiling, that is, without destroying its state. Such "natural protection" intrinsic single photon, can serve as a basis for the development of an "absolute" coding in future devices for encryption, in which no attempt at "hacking" can not remain unnoticed.

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