  One of the most striking non-classical features of quantum mechanics is in
the correlations it predicts between spatially separated measurements. In local
hidden variable theories, correlations are constrained by Bell inequalities,
but quantum correlations violate these. However, experimental imperfections
lead to "loopholes" whereby LHV correlations are no longer constrained by Bell
inequalities, and violations can be described by LHV theories. For example,
loopholes can emerge through selective detection of events. In this letter, we
introduce a clean, operational picture of multi-party Bell tests, and show that
there exists a non-trivial form of loophole-free post-selection. Surprisingly,
the same post-selection can enhance quantum correlations, and unlock a
connection between non-classical correlations and non-classical computation.
