 Speculative as it may seem, the question “what is quantum in quantum computing?” has significant practical consequences. One of the embarrassments of quantum computing is the paucity of quantum algorithms which have actually been discovered. It is almost certain that one of the reasons for this is the lack of a full understanding of what makes a quantum computer quantum (see also Preskill (1998) and Shor (2004)). As an ultimate answer to this question one would like to have something similar to Bell’s famous  theorem,  i.e., a succinct crisp statement of the fundamental difference between quantum and classical systems. Quantum computers, unfortunately, do not seem to allow such a simple characterisation (see Cuffaro 2017, 2018a). Quantum computing skeptics (Levin 2003) happily capitalise on this puzzle: If no one knows why quantum computers are superior to classical ones, how can we be sure that they are, indeed, superior?