  An obvious way to entangle two atoms located at remote locations is to
produce a pair of entangled photons half-way between the two atoms, to sent one
photon to each location and to subsequently map the photonic entanglement into
the atoms. The efficiency of this process is, however, fundamentally limited
due to overall transmission losses. We propose a method to herald the success
of the mapping operation in free space without destroying nor revealing the
stored quantum state. Interestingly for a Bell test, the heralding signal does
not open the detection loophole provided the measurement choice is performed
once the heralding is obtained only. We show through a detailed feasibility
study that this approach could provide an attractive alternative to Bell tests
where the atom--atom entanglement is created from atom--photon entanglement
using an entanglement swapping operation.
