Witnessing single-photon entanglement with local homodyne measurements:   analytical bounds and robustness to losses
  Single-photon entanglement is one of the primary resources for quantum networks, including quantum repeater architectures. Such entanglement can be revealed with only local homodyne measurements through the entanglement witness presented in [Morin et al. Phys. Rev. Lett. 110, 130401 (2013)]. Here, we provide an extended analysis of this witness by introducing analytical bounds and by reporting measurements confirming its great robustness with regard to losses. This study highlights the potential of optical hybrid methods, where discrete entanglement is characterized through continuous-variable measurements. 
Melvyn Ho, Olivier Morin, Jean-Daniel Bancal, Nicolas Gisin, Nicolas   Sangouard, Julien Laurat
quant-ph