Probable Pasts

"'The past, also, is quantum probabilistic. By what roads, what means, did history come to us?'"
-Poul Anderson, Genesis (New York, 2001), p. 135.

For practical purposes, at least, we assume a single fixed past but several possible futures. I cannot change the fact that I acted wrongly yesterday but can now decide how to act tomorrow. Of course, maybe the future is fixed but we do not know it yet. However, that view does not help us to make decisions now. Kant differentiated between practical and theoretical reason.

Quantum theory refers to a fundamental uncertainty not only about the future but even about the present positions of particles but does this extend even to the past? Of course, much of the past is unknown. Therefore, any theory about, e.g., why the Spanish Armada failed must be assessed for its plausibility or probability but that does not make it probabilistic in the quantum sense. We still think that a single sequence of events occurred even though we do not know what that sequence was.

The Beatles visited Elvis Presley and each remembered the details differently: Elvis met them at the door; someone else met them at the door and introduced them to Elvis inside etc. This means that no one now knows precisely how the meeting occurred, not that that past meeting existed/exists in some superimposed Schrodinger state. Or are quantum pasts, like quantum futures, supposed to radiate away from each single present?