In this contribution I consider the consequences of using quantum me- chanics in nanoscale technology. I argue that this use leads to a problem that poses a two-sided challenge for interpretations of quantum mechanics. Firstly I present the problem: engineers typically ascribe technical functions to artifacts; function ascrip- tions imply particular physical descriptions of artifacts, and quantum mechanics sometimes fails to reproduce these descriptions. This problem may be solved by adopting an interpretation of quantum mechanics. An interpretation turns quantum mechanics into a theory that gives richer physical descriptions and that may repro- duce the physical descriptions implied by function ascriptions. It can be shown, however, that not all interpretations fulfill this promise. Secondly I argue that these results amount to a two-sided challenge. It challenges philosophers of physics to provide an interpretation that gives nano-engineers rich enough quantum-mechanical descriptions to ascribe functions to artifacts. And it challenges engineers to help phi- losophers of physics with selecting tenable interpretations. Philosophers of physics are in need of tests for judging the different existing interpretations, and nano- engineers can provide such tests by requiring that interpretations should reproduce the function ascriptions to the artifacts they design. A nanoscale technology example I consider is quantum teleportation.
The best mathematical arguments against a realistic interpretation of quantum mechanics - that gives definite but partially unknown values to all observables - are analysed and shown to be based on reasoning that is not compelling. This opens the door for an interpretation that, while respecting the indeterministic nature of quantum mechanics, allows to speak of definite values for all observables at any time that are, however, only partially measurable. The analysis also suggests new ways to test the foundations of quantum theory.