  The notorious quantum measurement problem brings out the difficulty to
reconcile two quantum postulates: the unitary evolution of closed quantum
systems and the wave-function collapse after a measurement. This problematics
is particularly highlighted in the Wigner's friend thought experiment, where
the mismatch between unitary evolution and measurement collapse leads to
conflicting quantum descriptions for different observers. A recent no-go
theorem has established that the (quantum) statistics arising from an extended
Wigner's friend scenario is incompatible when one try to hold together three
innocuous assumptions, namely no-superdeterminism, parameter independence and
absoluteness of observed events. Building on this extended scenario, we
introduce two novel measures of non-absoluteness of events. The first is based
on the EPR2 decomposition, and the second involves the relaxation of the
absoluteness hypothesis assumed in the aforementioned no-go theorem. To prove
that quantum correlations can be maximally non-absolute according to both
quantifiers, we show that chained Bell inequalities (and relaxations thereof)
are also valid constraints for Wigner's experiment.
