  The security analysis of quantum key distribution is difficult to perform
when there is efficiency mismatch between various threshold detectors involved
in an experimental setup. Even the verification that the device actually
performs in the quantum domain, referred to as the task of entanglement
verification, is hard to perform. In this article we provide such an
entanglement-verification method for characterized detection-efficiency
mismatch. Our method does not rely on a cut-off of photon numbers in the
optical signal. It can be applied independently of the degrees of freedom
involved, thus covering, for example, efficiency mismatch in polarization and
time-bin modes, but also in spatial modes. The evaluation of typical
experimental scenarios suggests that an increase of detection-efficiency
mismatch will drive the performance of a given setup out of the quantum domain.
