I don't quite agree. The essential piece that transforms the study of Turing machines from mathematics into science is the Church-Turing thesis. And the Church-Turng thesis that is not deductive in any sense of the word.
Anyway, bringing this back to QC. It is believed that algorithms exist that can be computed by a QC that cannot feasibly be done by a classical computer, so QC also meets the ”deductive mathematical definition with applicable characteristics” bar as well.
Anyway, let me be the one bringing the discussion back to quantum computing this time. I don't think anybody in the world who could argue that study of entanglement - think Bell's theorem and CHSH inequality - isn't science. In fact, the 2022 Noble Prize for Physics was awarded to people who made foundational contributions on that field. I see Quantum Computing as a direct spiritual successor to that study.
A proper definition of science would be able to consider a study X and classify it as science or not science using only intrinsic properties of the study, not an extrinsic property like a known connection to the empirical world.