I used to have links to lectures explaining this, but they seem to have 404`ed.
The general approach is to view quantum computers as a series of quantum gates. Specifically, the CC-Not gate takes 3 inputs and, if the first 2 are true, it toggles the third. This is sufficient to build an arbitrary gate, including a binary adder.
I would try explaining how these gates might be constructed, but its been so long since I've studied it that I would probably butcher the explanation.
The general approach is to view quantum computers as a series of quantum gates. Specifically, the CC-Not gate takes 3 inputs and, if the first 2 are true, it toggles the third. This is sufficient to build an arbitrary gate, including a binary adder.
I would try explaining how these gates might be constructed, but its been so long since I've studied it that I would probably butcher the explanation.