Entanglement of neutral-atom chains by spin-exchange Rydberg interaction
  Conditions to achieve an unusually strong Rydberg spin-exchange interaction are investigated and proposed as a means to generate pairwise entanglement and realize a SWAP-like quantum gate for neutral atoms. Ground-state entanglement is created by mapping entangled Rydberg states to ground states using optical techniques. A protocol involving SWAP gate and pairwise entanglement operations is predicted to create global entanglement of a chain of $N$ atoms in a time that is independent of $N$. 
Xiao-Feng Shi, F. Bariani, and T. A. B. Kennedy
quant-ph physics.atom-ph