  Entanglement and non-Gaussianity are physical resources that are essential
for a large number of quantum-optics protocols. Non-Gaussian entanglement is
indispensable for quantum-computing advantage and outperforms its Gaussian
counterparts in a number of quantum-information protocols. The characterization
of non-Gaussian entanglement is a critical matter as it is in general highly
demanding in terms of resources. We propose a simple protocol based on the
Fisher information for witnessing entanglement in an important class of
non-Gaussian entangled states: photon-subtracted states. We demonstrate that
our protocol is relevant for the detection of non-Gaussian entanglement
generated by multiple photon-subtraction and that it is experimentally feasible
through homodyne detection.
