Designing an ergonomic phone interface can be grouped under communication design, thus art. Constructing a quantum computer using optics clearly falls into the physics department, at least until physics spins off an engineering department for quantum stuff, like it spun off mechanics and electronics in earlier centuries.

I consider the term "computer science" historically motivated and anachronistic. Similar to how old people would stereotypically describe their child's job as "something with computers", we muddled subtopics of various sciences together just because they're doing "something with computers".

With computing technology and methodology now permeating nearly all areas of science, art, and engineering, maybe it's time to tear down the computer science departments and reintegrate their pieces back into the appropriate departments.

Or maybe we shouldn't, for we would lose the extremely diverse curriculum that a CS degree includes.