A strong no-go theorem on the Wigner's friend paradox

Bong 2020: observer-independence priced, not ontology decided

what the source states

A "local friendliness" no-go theorem shows that if quantum evolution is controllable on the scale of an observer, then one of no-superdeterminism, locality, or absoluteness of observed events must fail — constraints "strictly stronger" than Bell's theorem — with a photonic proof-of-principle experiment in which a photon's path is deemed an observer.

what we infer

The experiment closest in spirit to the Zero Worlds dispute, and its honest reading is deflationary in both directions: it taxes theories committed to absolute observed events, but its "friend" is a photon path — a controlled information-processing system — so nothing here demonstrates that consciousness or first-person states play a causal role. Benchmark, not verdict.

limitations

• Proof-of-principle scale; extending 'observer' from a photon path to systems anyone would call an observer is the entire unresolved point.