 The quantum computer might be the theoretician’s dream, but as far as experimentalists are concerned, its realisation is a nightmare. The problem is that while some prototypes of the simplest elements needed to build a quantum computer have already been implemented in the laboratory, it is still an open question how to combine these elements into scalable systems (see Van Meter and Horsman 2013). Shor’s algorithm may break RSA encryption, but it will remain an anecdote if the largest number that it can factor is 15. In the circuit-based model the problem is to achieve a scalable quantum system that at the same time will allow one to (1) robustly represent quantum information with (2) a time to decoherence significantly longer than the length of the computation, (3) implement a universal family of unitary transformations, (4) prepare a fiducial initial state, and (5) measure the output result (these are DiVincenzo (2000)’s five criteria). Alternative paradigms may trade some of these requirements with others, but the gist will remain the same, i.e., one would have to achieve control of one’s quantum system in such a way that the system will remain “quantum” albeit macroscopic or at least mesoscopic in its dimensions.