Foundations of Quantum Programming

3.4 Classical recursion in quantum programming

The notion of recursion allows the programming of repetitive tasks without a large number of similar steps to be specified individually. In the previous sections, we have studied the quantum extension of the while-language, which provides a program construct, namely the quantum while-loop, to implement a special kind of recursion – iteration – in quantum computation. The general form of recursive procedure has been widely used in classical programming. It renders a more powerful technique than iteration, in which a function can be defined, directly or indirectly, in terms of itself. In this section, we add the general notion of recursion into the quantum while-language in order to specify procedures ...