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Quantum information science is an area of study based on the idea that information science depends on quantum effects in physics. It includes theoretical issues in computational models as well as more experimental topics in quantum physics including what can and cannot be done with
quantum informationIn quantum mechanics, quantum information is physical information that is held in the "state" of a quantum system. The most popular unit of quantum information is the qubit, a twolevel quantum system...
. The term
quantum information theory is sometimes used, but it fails to encompass experimental research in the area.
Subfields include:
 Quantum computing
A quantum computer is a device for computation that makes direct use of quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. Quantum computers are different from traditional computers based on transistors...
, which deals on the one hand with the question how and whether one can build a quantum computerA quantum computer is a device for computation that makes direct use of quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. Quantum computers are different from traditional computers based on transistors...
and on the other hand, algorithms that harness its power (see quantum algorithmIn quantum computing, a quantum algorithm is an algorithm which runs on a realistic model of quantum computation, the most commonly used model being the quantum circuit model of computation. A classical algorithm is a finite sequence of instructions, or a stepbystep procedure for solving a...
)
 Quantum complexity theory
Quantum complexity theory is a part of computational complexity theory in theoretical computer science. It studies complexity classes defined using quantum computers and quantum information which are computational models based on quantum mechanics...
 Quantum cryptography
Quantum key distribution uses quantum mechanics to guarantee secure communication. It enables two parties to produce a shared random secret key known only to them, which can then be used to encrypt and decrypt messages...
and its generalization, quantum communication
 Quantum error correction
Quantum error correction is used in quantum computing to protect quantum information from errors due to decoherence and other quantum noise. Quantum error correction is essential if one is to achieve faulttolerant quantum computation that can deal not only with noise on stored quantum...
 Quantum communication complexity
 Quantum entanglement
Quantum entanglement occurs when electrons, molecules even as large as "buckyballs", photons, etc., interact physically and then become separated; the type of interaction is such that each resulting member of a pair is properly described by the same quantum mechanical description , which is...
, as seen from an informationtheoretic point of view
 Quantum dense coding
 Quantum teleportation
Quantum teleportation, or entanglementassisted teleportation, is a process by which a qubit can be transmitted exactly from one location to another, without the qubit being transmitted through the intervening space...
is one wellknown quantum information processing operation which reliably transfers an unknown quantum state from one point to another distant point, destroying the original state in the process.
See also
 No communication theorem
 Quantum decision tree complexity
External links
 Quantiki – quantum information science portal and wiki.
 ERAPilot QIST WP1 European roadmap on Quantum Information Processing and Communication
 QIIC – Quantum Information, Imperial College London.
 QIP – Quantum Information Group, University of Leeds. The quantum information group at the University of Leeds is engaged in researching a wide spectrum of aspects of quantum information. This ranges from algorithms, quantum computation, to physical implementations of information processing and fundamental issues in quantum mechanics. Also contains some basic tutorials for the lay audience.
 CQIST Center for Quantum Information Science & Technology at the University of Southern California
 CQuIC Center for Quantum Information and Control, including theoretical and experimental groups from University of New Mexico, University of Arizona.