Spatial Entanglement of Bosons in Thermal Equilibrium
  We investigate spatial entanglement in a system of spinless non-interacting bosons in a one dimensional harmonic trap described by the grand canonical ensemble. We find the lower bound for the amount of spatial entanglement contained in the average state of two bosons in the trap and show that it exists for arbitrary high temperatures. 
Dagomir Kaszlikowski, Andreas Keil, Marcin Wiesniak, Frederic H.   Willenboordse