Entanglement in the XY spin chain

  title={Entanglement in the XY spin chain},
  author={Alexander Its and Bufan Jin and Vladimir E. Korepin},
  journal={Journal of Physics A},
We consider the entanglement in the ground state of the XY model of an infinite chain. Following Bennett, Bernstein, Popescu and Schumacher, we use the entropy of a sub-system as a measure of entanglement. Vidal, Latorre, Rico and Kitaev have conjectured that the von Neumann entropy of a large block of neighbouring spins approaches a constant as the size of the block increases. We evaluate this limiting entropy as a function of anisotropy and transverse magnetic field. We use the methods based… 

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