  The creation and detection of entanglement in solid state electronics is of
fundamental importance for quantum information processing. We prove that
second-order quantum correlations can be always interpreted classically and
propose a general test of entanglement based on the violation of a classically
derived inequality for continuous variables by fourth-order quantum correlation
functions. Our scheme provides a way to prove the existence of entanglement in
a mesoscopic transport setup by measuring higher order cumulants without
requiring the additional assumption of a single charge detection
