Why Born Probabilities?
18Michael Weissman (University of Illinois Urbana-Champaign)
https://simons.berkeley.edu/talks/why-born-probabilities-na-also-fine-kind-topic-though-fun
Quantum Physics and Statistical Causal Models
The origin of the Born probability rule in unitary (Many Worlds) quantum mechanics is obscure. Many formal arguments claim to show it is the only consistent rule but all explicitly or implicitly assume that the probabilities must be expressible as products of probabilities of events. I.e. the probability that Schroedinger's cat is alive does not change after the experiment depending on whether it has quantum fleas. This rule is needed for the world to make sense but does not flow naturally from quantum dynamics. Mallah* has proposed a many-computations approach in which the rule could follow naturally if the quantum state we usually describe is superimposed on a background of quantum noise following only the unitary dynamics. I suggest that the background is expected, and our low-entropy component remains the only mystery. https://arxiv.org/abs/0709.0544