The retrosignaling described below does not lead to paradoxes like the grandfather paradox because of its stochastic nature.
From A, many possible paths with A as the source are generated. This are the possible paths of a particle originating from A.
The paths end up at possible endpoints B, B, … . Each B[i] could be the endpoint for several paths. (In a path-integral formulation, each path “carries” on a channel a (changing) unit (circle) complex number (UCN).
From each B[i], retrosignals (backwards-in-time signals) are sent on path backchannels to A. (These are “weights” – computed as the modulus of the sum of UCNs received at B[i] – carried by each path backwards in time to A.
A gets all these retrosignalled weights (effectively resulting in a probability distribution on all paths) and selects a single path. (This occurs at the very same time that it generated the paths.)
Result: There is only one B[i*], and only one path leading to B[i*].
The paths are like A‘s litter (of children). It gets signals from the future on the prospects for each child. A kills off all its children but one. The quantum substrate is a cruel world.
In the EPR experiment (where a source S transmits a particle with a path to endpoint A and transmits a particle with a path to endpoint B): A signal with information about A is backchanneled on the first path to S. A signal with information about B is backchanneled on the second path to S. These retrosignals are received at S simultaneously, and are used by S to stochastically select the states of the (heterogeneous) twin particles.The quantum substrate has a weak clairvoyance.