The quasi-particle picture and its breakdown after local quenches in conformal field theories

We discuss the dynamics of (Rényi) mutual information, logarithmic negativity, and (Rényi) reflected entropy after exciting the ground state by a local operator in (1+1)d conformal field theories. In particular, we contrast "integrable" and "chaotic" conformal field theories, by looking at the quasi-particle picture and its possible breakdown. In comparing the calculations in the two classes of theories, we are able to identify the dynamical mechanism for the breakdown of the quasi-particle picture in 2D conformal field theories. Intriguingly, we also find preliminary evidence that our general lessons apply to quantum systems considerably distinct from conformal field theories, such as integrable and chaotic spin chains, suggesting a  universality of entanglement dynamics in non-equilibrium systems.