Multi-qubit entanglement in bi-directional chiral waveguide QED
  We study the generation of entanglement induced by a single-photon Gaussian wavepacket in multi-atom bi-directional waveguide QED. In particular, we investigate the effect of increasing the number of atoms on the average pairwise entanglement. We demonstrate by selecting smaller decay rates and in chiral waveguide settings, that both entanglement survival times and maximum generated entanglement can be increased by at least a factor of 3/2, independent of the number of atoms. In addition, we analyze the influence of detuning and delays on the robustness of the generated entanglement. There are potential applications of our results in entanglement based multi-qubit quantum networks 
Imran M. Mirza, John C. Schotland
quant-ph