Wouldn't questioning those pre-existing notions be the first step towards constructing such a machine? It sounds silly to dismiss the idea time could go backwards because we don't have any machines that work that way, since that typically how all ideas work before we implement them.

Maybe all that quantum nonsense we can't explain is due to some type of time travel we don't comprehend.

If only we had Tony Stark to help build some sort of a “quantum GPS”.