A quantum register of N qubits can therefore store 2 N numbers in quantum superposition. Because a qubit is capable of being in both 0 and 1 states simultaneously, operations on a qubit in superposition effectively act on both values at the same time. In classical computer science, an algorithm is defined as being the specification of a set of instructions. These instructions can be mechanically applied to give the solution to any given instance of a problem. A quantum algorithm is a set of instructions for a quantum computer, however, unlike algorithms in classical computer science their results cannot be guaranteed.
Most quantum algorithms involve a series of quantum state transformations followed by a measurement.
Currently very few quantum algorithms are known and no general design methodology exists for their construction.