  We propose Bell inequalities for discrete or continuous quantum systems which
test the compatibility of quantum physics with an interpretation in terms of
deterministic hidden-variable theories. The wave function collapse that occurs
in a sequence of quantum measurements enters the upper bound via the concept of
quantum conditional probabilities. The resulting hidden-variable inequality is
applicable to an arbitrary observable that is decomposable into a weighted sum
of non-commuting projectors. We present local and non-local examples of
violation of generalized Bell inequalities in phase space, which sense the
negativity of the Wigner function.

Quantum Physics