A quantum computer is "a sensor" in the same sense that every laptop is "an electronics experiment". A quantum computer still fits your model because you arbit

A quantum computer is "a sensor" in the same sense that every laptop is "an electronics experiment". A quantum computer still fits your model because you arbitrarily represent anything with an alphabet of quantum states, automatically manipulate it with a quantum algorithm, and map back the result at the end so we learn something about whatever. I do not see the contradiction.