  Is it possible that a measurement of a spin component of a spin-1/2 particle
yields the value 100? In 1988 Aharonov, Albert and Vaidman argued that upon
pre- and postselection of particular spin states, weakening the coupling of a
standard measurement procedure ensures this paradoxical result. This
theoretical prediction, called weak value, was realized in numerous
experiments, but its meaning remains very controversial, since its "anomalous"
nature, i.e. the possibility to exceed the eigenvalues range, as well as its
"quantumness" are debated. We address these questions by presenting the first
experiment measuring anomalous weak values with just a single click, without
any statistics. The measurement uncertainty is significantly smaller than the
gap between the measured weak value and the nearest eigenvalue. Beyond
clarifying the meaning of weak values, this result represents a breakthrough in
understanding quantum measurement foundations, paving the way to further
applications of weak values to quantum photonics.
