Entanglement and correlation functions following a local quench: a conformal field theory approach

Abstract. We show that the dynamics resulting from preparing a onedimensional quantum system in the ground state of two decoupled parts, then joined together and left to evolve unitarily with a translational invariant Hamiltonian (a local quench), can be described by means of quantum field theory. In the case when the corresponding theory is conformal, we study the evolution of the entanglement entropy for different bi-partitions of the line. We also consider the behavior of one- and two-point correlation functions. All our findings may be explained in terms of a picture, that we believe to be valid more generally, whereby quasiparticles emitted from the joining point at the initial time propagate semiclassically through the system. Entanglement and correlation functions following a local quench: a CFT approach 2 1. Introduction. The understanding of the degree of entanglement in extended quantum systems has prompted an enormous effort in a field at the border of condensed matter physics, quantum information theory, and quantum field theory. It would take too long to mention all the topics and problems addressed so far: we refer the reader to a recent

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