Evolution of entanglement entropy following a quantum quench : Analytic results for the XY chain in a transverse magnetic field

By M. Fagotti, Pasquale Calabrese. 2008

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The non-equilibrium evolution of extended quantum systems is one of the most challenging problems of contemporary research in theoretical physics. The subject is in a renaissance era after the experimental realization [1] of cold atomic systems that can evolve out of equilibrium in the absence of any dissipation and with high degree of tunability of Hamiltonian parameters. A strongly limiting factor for a better understanding of these phenomena is the absence of effective numerical methods to simulate the dynamics of quantum systems. For methods like time dependent density matrix renormalization group (tDMRG) [2] this lack of efficiency has been traced back [3] to a too fast increasing of the entanglement entropy between parts of the whole system and the impossibility for a classical computer to store and manipulate such large amount of quantum information. This observation partially moved the interest from the study of local observables to the understanding of the evolution of the entanglement entropy and in particular to its growth with time [5, 6]. Based on early results from conformal field theory [6, 7] and on exact/numerical ones for simple solvable model [6, 8] it is widely accepted [3] that the entanglement entropy grows linearly with time for a so called global quench (i.e. when the initial state differs globally from the ground state and the excess of energy is extensive), while at most logarithmically for a local one (i.e. when the the initial state has only a local difference with the ground state and so a little excess of energy). As a consequence a local quench is simulable by means of tDMRG, while a global one is not. However, despite this fundamental interest and a large effort of the community, still analytic results are lacking. In this letter we fill this gap providing the analytic expression of the entanglement entropy at any time in the limit of a large block for the XY chain in a transverse magnetic field described by the Hamiltonian

Subfields: Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/b7a49516b2b6415f2ef8d92091c5ff75e7b78d0e

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In Atomic and Molecular Physics, and Optics

  1. Pasquale Calabrese
  2. A. Nahum
  3. J. Cardy
  4. M. Fagotti
  5. V. Alba
  6. Matthew Fisher
  7. F. Essler
  8. V. Khemani

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