Thought experiment: if the quantum computer selects the one parallel reality with the answer you need to produce, as you say above, and does so merely by observation/wave collapse, wasn't the information obtained without expending work? That's zero point energy derived from the Heisenberg principle.

(hint: Hawking shows information cannot be destroyed or created without proportional energy preservation - https://en.wikipedia.org/wiki/Black_hole_information_paradox)