Quantum theory, the Church-Turing principle and the universal quantum computer

During the last few decades, an extensive development of the theory of computing machines has occurred. On an intuitive basis, a computing machine is considered to be any physical system whose dynamical evolution takes it from one of a set of 'input' states to one of a set of 'output' states. For a classical deterministic system the measured output label is a definite function f of the prepared input label. However, quantum computing machines, and indeed classical stochastic computing machines, do not 'compute functions' in the considered sense. Attention is given to the universal Turing machine, the Church-Turing principle, quantum computers, the properties of the universal quantum computer, and connections between physics and computer science.