# Quantum information science

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Quantum information science is an interdisciplinary field that seeks to understand the analysis, processing, and transmission of information using quantum mechanics principles. It combines the study of Information science with quantum effects in physics. It includes theoretical issues in computational models and more experimental topics in quantum physics, including what can and cannot be done with quantum information. The term quantum information theory is also used, but it fails to encompass experimental research, and can be confused with a subfield of quantum information science that addresses the processing of quantum information.

## Scientific and engineering studies

To understand quantum teleportation, quantum entanglement and the manufacturing of quantum computer hardware requires a thorough understanding of quantum physics and engineering. Since 2010s, there has been remarkable progress in the manufacturing quantum computers, with companies like Google and IBM investing heavily in quantum computer hardware research. Today, it is possible to build a quantum computer with more than 100 qubits. However, the error rate is very large due to the lack of material suitable for the manufacture of quantum computers. Majorana fermions may be one of the key materials lacking.[ citation needed ]

Devices for quantum cryptography have already been commercialized. There is an old cipher called a one time pad widely used among spies in the Cold War era. It uses a long sequence of random keys. If two people exchanged the same random keys safely, it is possible to decrypt a one time pad only by accident. However, key exchanging problems can be solved by using quantum entangled particle pairs in the exchange. Quantum mechanical laws such as the no cloning theorem and wave function collapse provide the basis for secure exchange of random keys. Therefore the manufacturing of devices that can transport quantum entangled particles is an important scientific and engineering goal.

Programming languages for quantum computers are also needed. Q Sharp and Qiskit are popular quantum programming languages.

Quantum algorithm and quantum complexity theory are two of the subjects in algorithms and computational complexity theory. In 1994, mathematician Peter Shor published his prime factorization algorithm. If one has a 1,000-qubit quantum computer, one can threaten most widely used ciphers such as RSA and ECC by using Shor's algorithm. It can result in serious security problems for many countries. Therefore, his paper triggered a lot of investment in quantum computing research. Many mathematicians and cryptologists are preparing to enter the quantum computing era. See post quantum cryptography.

## Related Research Articles

Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic processes and development of both hardware and software. It has scientific, engineering, mathematical, technological and social aspects. Major computing disciplines include computer engineering, computer science, cybersecurity, data science, information systems, information technology and software engineering.

Quantum computing is the exploitation of collective properties of quantum states, such as superposition and entanglement, to perform computation. The devices that perform quantum computations are known as quantum computers. They are believed to be able to solve certain computational problems, such as integer factorization, substantially faster than classical computers. The study of quantum computing is a subfield of quantum information science. It is likely to expand in the next few years as the field shifts toward real-world use in pharmaceutical, data security and other applications.

Quantum information is the information of the state of a quantum system. It is the basic entity of study in quantum information theory, and can be manipulated using quantum information processing techniques. Quantum information refers to both the technical definition in terms of Von Neumann entropy and the general computational term.

In quantum computing, a qubit  or quantum bit is the basic unit of quantum information—the quantum version of the classic binary bit physically realized with a two-state device. A qubit is a two-state quantum-mechanical system, one of the simplest quantum systems displaying the peculiarity of quantum mechanics. Examples include the spin of the electron in which the two levels can be taken as spin up and spin down; or the polarization of a single photon in which the two states can be taken to be the vertical polarization and the horizontal polarization. In a classical system, a bit would have to be in one state or the other. However, quantum mechanics allows the qubit to be in a coherent superposition of both states simultaneously, a property that is fundamental to quantum mechanics and quantum computing.

This is a timeline of quantum computing.

While logical inference and mathematical proof had existed previously, in 1931 Kurt Gödel proved with his incompleteness theorem that there are fundamental limitations on what statements could be proved or disproved.

Anton Zeilinger is an Austrian quantum physicist who in 2008 received the Inaugural Isaac Newton Medal of the Institute of Physics (UK) for "his pioneering conceptual and experimental contributions to the foundations of quantum physics, which have become the cornerstone for the rapidly-evolving field of quantum information". Zeilinger is professor of physics at the University of Vienna and Senior Scientist at the Institute for Quantum Optics and Quantum Information IQOQI at the Austrian Academy of Sciences. Most of his research concerns the fundamental aspects and applications of quantum entanglement.

The Bell states or EPR pairs are specific quantum states of two qubits that represent the simplest examples of quantum entanglement; conceptually, they fall under the study of quantum information science. The Bell states are a form of entangled and normalized basis vectors. This normalization implies that the overall probability of the particle being in one of the mentioned states is 1: . Entanglement is a basis-independent result of superposition. Due to this superposition, measurement of the qubit will collapse it into one of its basis states with a given probability. Because of the entanglement, measurement of one qubit will assign one of two possible values to the other qubit instantly, where the value assigned depends on which Bell state the two qubits are in. Bell states can be generalized to represent specific quantum states of multi-qubit systems, such as the GHZ state for 3 or more subsystems.

Charles Henry Bennett is a physicist, information theorist and IBM Fellow at IBM Research. Bennett's recent work at IBM has concentrated on a re-examination of the physical basis of information, applying quantum physics to the problems surrounding information exchange. He has played a major role in elucidating the interconnections between physics and information, particularly in the realm of quantum computation, but also in cellular automata and reversible computing. He discovered, with Gilles Brassard, the concept of quantum cryptography and is one of the founding fathers of modern quantum information theory.

Quantum networks form an important element of quantum computing and quantum communication systems. Quantum networks facilitate the transmission of information in the form of quantum bits, also called qubits, between physically separated quantum processors. A quantum processor is a small quantum computer being able to perform quantum logic gates on a certain number of qubits. Quantum networks work in a similar way to classical networks. The main difference is that quantum networking, like quantum computing, is better at solving certain problems, such as modeling quantum systems.

The Centre for Quantum Technologies (CQT) in Singapore is a Research Centre of Excellence hosted by the National University of Singapore. The Centre brings together physicists, computer scientists and engineers to do basic research on quantum physics and to build devices based on quantum phenomena. Experts in quantum technologies are applying their discoveries in computing, communications and sensing.

Quantum cryptography is the science of exploiting quantum mechanical properties to perform cryptographic tasks. The best known example of quantum cryptography is quantum key distribution which offers an information-theoretically secure solution to the key exchange problem. The advantage of quantum cryptography lies in the fact that it allows the completion of various cryptographic tasks that are proven or conjectured to be impossible using only classical communication. For example, it is impossible to copy data encoded in a quantum state. If one attempts to read the encoded data, the quantum state will be changed due to wave function collapse. This could be used to detect eavesdropping in quantum key distribution. It's contrary combative used culture couldn't be a quantum.

The Centre for Quantum Computation (CQC) is an alliance of quantum information research groups at the University of Oxford. It was founded by Artur Ekert in 1998.

Being a component part of network science the study of quantum complex networks aims to explore the impact of complexity science and network architectures in quantum systems. According to quantum information theory it is possible to improve communication security and data transfer rates by taking advantage of quantum mechanics. In this context the study of quantum complex networks is motivated by the possibility of quantum communications being used on a massive scale in the future. In such case it is likely that quantum communication networks will acquire non trivial features as is common in existing communication networks today.

The DiVincenzo criteria are conditions necessary for constructing a quantum computer, conditions proposed in 2000 by the theoretical physicist David P. DiVincenzo, as being those necessary to construct such a computer—a computer first proposed by mathematician Yuri Manin, in 1980, and physicist Richard Feynman, in 1982—as a means to efficiently simulate quantum systems, such as in solving the quantum many-body problem.

In quantum computing, quantum supremacy or quantum advantage is the goal of demonstrating that a programmable quantum device can solve a problem that no classical computer can solve in any feasible amount of time. Conceptually, quantum supremacy involves both the engineering task of building a powerful quantum computer and the computational-complexity-theoretic task of finding a problem that can be solved by that quantum computer and has a superpolynomial speedup over the best known or possible classical algorithm for that task. The term was coined by John Preskill in 2012, but the concept of a quantum computational advantage, specifically for simulating quantum systems, dates back to Yuri Manin's (1980) and Richard Feynman's (1981) proposals of quantum computing. Examples of proposals to demonstrate quantum supremacy include the boson sampling proposal of Aaronson and Arkhipov, D-Wave's specialized frustrated cluster loop problems, and sampling the output of random quantum circuits.

Harry Buhrman is a Dutch computer scientist, currently Professor of algorithms, complexity theory, and quantum computing at the University of Amsterdam (UvA), group leader of the Quantum Computing Group at the Centrum Wiskunde & Informatica (CWI), and executive director of QuSoft, the Dutch research center for quantum software.

Continuous-variable quantum information is the area of quantum information science that makes use of physical observables, like the strength of an electromagnetic field, whose numerical values belong to continuous intervals. One primary application is quantum computing. In a sense, continuous-variable quantum computation is "analog", while quantum computation using qubits is "digital." In more technical terms, the former makes use of Hilbert spaces that are infinite-dimensional, while the Hilbert spaces for systems comprising collections of qubits are finite-dimensional. One motivation for studying continuous-variable quantum computation is to understand what resources are necessary to make quantum computers more powerful than classical ones.

Paul A. Benioff is an American physicist who helped pioneer the field of quantum computing. Benioff is best known for his research in quantum information theory during the 1970s and 80s that demonstrated the theoretical possibility of quantum computers by describing the first quantum mechanical model of a computer. In this work, Benioff showed that a computer could operate under the laws of quantum mechanics by describing a Schrödinger equation description of Turing machines. Benioff's body of work in quantum information theory has continued on to the present day and has encompassed quantum computers, quantum robots, and the relationship between foundations in logic, math, and physics.

Quantum Computing: A Gentle Introduction is a textbook on quantum computing. It was written by Eleanor Rieffel and Wolfgang Polak, and published in 2011 by the MIT Press.

## References

• Nielsen, Michael A.; Chuang, Isaac L. (June 2012). Quantum Computation and Quantum Information (10th anniversary ed.). Cambridge: Cambridge University Press. ISBN   9780511992773. OCLC   700706156.
• Quantiki quantum information science portal and wiki.
• ERA-Pilot 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.
• mathQI Research Group on Mathematics and Quantum Information.
• 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.
• CQT Centre for Quantum Technologies at the National University of Singapore
• CQC2T Centre for Quantum Computation and Communication Technology
• QST@LSU Quantum Science and Technologies Group at Louisiana State University