Quantum computation studies computational systems (quantum computers) that make direct use of quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. Quantum computers are different from digital binary electronic computers based on transistors. While common digital computing requires that data be encoded into binary digits (bits), each of which is always in one of two defined states (0 or 1), quantum computation uses quantum bits, which may be in overlapping of states. A Turing quantum machine is a theoretical model of such a computer, and is also known as the universal quantum computer. The field of quantum computing was initiated by the work of Paul Benioff and Yuri Manin in 1980, Richard Feynman in 1982 and David Deutsch in 1985. A quantum computer with spins as quantum bits was also formulated to be used as quantum space-time in 1968.
Beginning in 2017, the development of real quantum computers is still in its infancy, but experiments have been carried out in which quantum computational operations are executed on a very small number of quantum bits. Both practical and theoretical research continues and many national governments and military agencies are funding quantum computing research in an additional effort to develop quantum computers for civil, business, commercial, environmental and national security purposes, such as cryptanalysis. There is a small quantum computer of 5 qubit and is available for fans to experiment with the IBM quantum experience project.
In theory, large-scale quantum computers could solve certain problems much more quickly than any classical computer using even the best known algorithms such as integer factorization using the Shor algorithm or the simulation of many-body quantum systems. There are quantum algorithms, such as the Simon algorithm, that run faster than any possible classical probabilistic algorithm. A classical computer could in principle (with exponential resources) simulate a quantum algorithm, since quantum computation does not violate Church-Turing's thesis.