  We present a universal mechanism that, acting on any target qubit, propagates
it to the state it had T time units before the experiment started. This
protocol works by setting the target on a superposition of flight paths, where
it is acted on by uncharacterized, but repeatable, quantum operations.
Independently of the effect of each of these individual operations on the
target, the successful interference of the paths causes it to leap to its past
state. We prove that, for generic interaction effects, the system will reach
the desired state with probability 1 after some finite number of steps.
