Reduced density matrices and entanglement entropy in free lattice models

Jun 9, 2009
Published in:
  • J.Phys.A 42 (2009) 50, 504003
  • Published: Dec 2, 2009
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Abstract: (IOP)
We review the properties of reduced density matrices for free fermionic or bosonic many-particle systems in their ground state. Their basic feature is that they have a thermal form and thus lead to a quasi-thermodynamic problem with a certain free-particle Hamiltonian. We discuss the derivation of this result, the character of the Hamiltonian and its eigenstates, the single-particle spectra and the full spectra, the resulting entanglement and in particular the entanglement entropy. This is done for various one- and two-dimensional situations, including also the evolution after global or local quenches.