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Quantum information processing and cryptography

Quantum information processing is a new trend in the field of information processing, computation, communication and security. Peculiar laws of quantum physics and properties of the microscopic quantum world can be harnessed to solve problems that cannot be solved classically at all or to solve them more efficiently. Applications include e.g. unconditionally secure key distribution, exponential speed-up of algorithms for some problems (integer factorization, discrete logarithm problem, database search), increasing capacity of communication channels and many others.

While the basic unit of classical information (a (classical) bit) has only two possible values, the basic unit of quantum information (a quantum bit (qubit)) has uncountable many possible values. Quantum information processing, communication and cryptography make use of weird, and often seemingly magical, phenomena as quantum entanglement and non-local effects. One of very interesting applications of these phenomena is quantum teleportation.

Quantum teleportation enables us to transfer indirectly a quantum state. More precisely, it enables the sender to send infomation describing the state in such a way that the receiver can create, using this information, a state identical to it. Moreover, quantum teleportation can be used even if no information about the object which is to be sent is known. For quantum teleportation to be possible, both parties have to share an entangled quantum state. The transferred information consists of a quantum part and a classical part. The quantum part is transferred immediately after joint measurement of the teleported state and one part of the entangled state. The (classical) result of the sender's measurement, which is represented by two bits, has to be then transferred somehow (e. g. by phone) so that the receiver is able to fully reconstruct the transferred state. Quantum teleportation cannot be used for faster-than-light communication because without the additional classical information the receiver obtains only the completelely mixed state (in other words, the transferred state is perfectly encrypted) and further operations, depending on the sender's measurement result, have to be performed in order to transform it into the state which has been sent.


Main research directions

The following topics are studied in Laboratory of Quantum Information Processing and Cryptography (LQIPC):

Information for students

Quantum information processing is an important field due to five main reasons:

Quantum information processing is a vivid field with many research topics. Students can participate in the activities of LQIPC either by choosing such a topic for their master's (bachelor) thesis of by entering Ph.D. study.

The main condition for this participation is the interest in quantum information processing and possibly also in classical cryptography. Other prerequisities include the ability to work individually and good mathematical background. While working in LQIPC, students are expected, with the help of older students, to deepen their knowledge of Informatics and Mathematics. The necessary knowledge of quantum Physics basics can be acquired withing two semesters.


Research team members


International cooperation

LQIPC has established a close cooperation (e.g. common projects, visits) with Slovak Academy of Sciences in Bratislava, University of Pécs, IST Lisbon, University of Bristol, NU Singapore, University of Tokyo, Kyoto University and KAIST Seoul. A close cooperation with ARC Seibersdorf is intended. Within faculty LQIPC collaborates with Laboratory of Security and Applied Cryptography.

LQIPC is one of the main organizers of the regular workshop CEQIP (Central European Quantum information Processing) and participates in organizing one of the most significant conferences in the field of quantum information processing - AQIS (Asian Conference on Quantum Information Science) which takes place annually in Asian countries (Japan, China, Korea).


Results

The members of LQIPC have achieved many theoretical results concerning the properties of entanglement, quantum primitives and their universality and the potential of programmable quantum processors. A new typed imperative programming language has been developed which enables us to combine classical and quantum computation. In quantum cryptography private quantum channels have been analyzed and a secure quantum protocol for achieving anonymity has been proposed.


Solved projects:


Contact:

prof. RNDr. Jozef Gruska, DrSc.
Phone: +420 549 49 4592
E-mail: gruska@fi.muni.cz
http://www.fi.muni.cz/usr/gruska/
http://qicz.fi.muni.cz/