Perfect state transfer in XX chains induced by boundary magnetic fields
  A recent numerical study of short chains found near-perfect quantum state transfer between the boundary sites of a spin-1/2 XX chain if a sufficiently strong magnetic field acts on these sites. We show that the phenomenon is based on a pair of states strongly localized at the boundaries of the system and provide a simple quantitative analytical explanation. 
Thorben Linneweber, Joachim Stolze, G\"otz S. Uhrig
quant-ph