  A loophole-free violation of Bell inequalities is of fundamental importance
for demonstrating quantum nonlocality and long-distance device-independent
secure communication. However, transmission losses represent a fundamental
limitation for photonic loophole-free Bell tests. A local precertification of
the presence of the photons immediately before the local measurements may solve
this problem. We show that local precertification is feasible by integrating
three current technologies: (i) enhanced single-photon down-conversion to
locally create a flag photon, (ii) nanowire-based superconducting single-photon
detectors for a fast flag detection, and (iii) superconducting transition-edge
sensors to close the detection loophole. We carry out a precise space-time
analysis of the proposed scheme, showing its viability and feasibility.
