Zhang finds probability in five Born-rule derivations — SkimNews
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- Jiaxuan Zhang spent about two years examining five influential derivations of the Born rule, testing whether their starting assumptions were purely deterministic; she found probability embedded in them.
- Born rule serves as both a recipe for turning quantum information into outcome probabilities and a founding postulate of quantum mechanics, rather than something the original theory derived.
- Born rule derivations examined by Zhang drew on symmetry, quantum entanglement, decision theory and inhabitants of a quantum multiverse, spanning multiple interpretations of the theory.
- Additivity was found to be indispensable in some form to all five derivations in Zhang’s analysis; in dice terms, the probabilities for six possible results must sum to 100%.
- Augusto Smerzi said exposing additivity clarifies where quantum probabilities come from, but does not explain why nature obeys the assumptions and does not rule out a deeper explanation.
- Zhang said more Born-rule derivations remain to be analyzed and that her current result does not support deriving the probabilistic rule solely from deterministic principles, though she sees a small chance of deterministic foundations.
Why it matters: For researchers seeking deterministic quantum mechanics, the five derivations Zhang examined share a common obstacle: each depends on some version of additivity. Her result constricts that program rather than ending it, and Smerzi says it still leaves unexplained why nature obeys those assumptions.
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