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**Quantum Information**

Quantum Information is a new interdisciplinary domain which emerged at the end of XX century. It is a marriage of quantum mechanics – the most successful theory, describing Nature, and computer science. While already the standard information technology has employed quantum mechanical nature of matter and light to process information (e.g. in lasers and transistors), the very information was virtually the same as in ancient time, as it consisted of bits. The quantum information offers a revolutionary concept of “quantum bits”, the way they are processed has no analogues in traditional IT science. It turned out that operating with qubits is a promising idea, which allows for two major advances:

- Quantum cryptography
- Quantum computer

Standard bits can be carried by various systems, such as abacus, mechanical computing machines, or the present day silicon based technology. Similarly the quantum bits can be implemented on various physical systems, such as photons, electrons or atoms. In particular, the same optical fibers, which are used in telecom networks can be used to send qubits. However, the quantum bits are fragile to external disturbance, therefore, at the moment, one cannot send a qubit for arbitrary distance.

The main present-day challenges of quantum cryptography is to extend the distance at which secure communication can be carried out (at present around 100 km), and to build a scalable quantum computer. There are experimental demonstrations of quantum computation performed on several qubits, however it still a challenge to enlarge the number of qubits. To this end, scientists are identifying more and more systems, which are suitable to implement quantum bits, such as atomic arrays, quantum dot arrays, microcavities etc.

Quantum information has its roots in philosophical debates on paradoxes exhibited by quantum mechanics, which seems to be in contradiction with our common sense. Due to discoveries quantum information, these paradoxes are nowadays not only a subject of a philosophical reflection, but have become a “fuel” for practical applications, which are of interest of major companies such as Hewlett Packard, Microsoft, Toshiba, NEC and others, which invest into quantum technologies.

Last but not least: apart from its main goal – processing of quantum information - the quantum information domain can be also helpful for standard computer science. Namely the famous Moore’s law indicates, sooner or later, the basing we will need to have transistor of the size comparable to that of atoms so that the quantum effects will inevitably enter, and whether we want it or not, the quantum technology will dominate IT. We shall therefore need to learn how to control the quantum systems in optimal way, which is just a basic branch of quantum information domain.