Dissipative quasiparticle picture for quadratic Markovian open quantum systems

Correlations between different regions of a quantum many-body system can be quantified through measures based on entropies of (reduced) subsystem states. For closed systems, several analytical and numerical tools, e.g., hydrodynamic theories or tensor networks, can accurately capture the time evolution of subsystem entropies, thus allowing for a profound understanding of the unitary dynamics of quantum correlations. However, these methods either cannot be applied to open quantum systems or do not permit an efficient computation of quantum entropies for mixed states. Here we make progress in solving this issue by developing a dissipative quasiparticle picture- describing quantum entropies and the mutual information in the limit of large space-time coordinates with their ratio being fixed-and showing its validity for quadratic open quantum systems. Our results demonstrate that the open quantum many-body dynamics of correlations can be understood in terms of propagating (dissipative) quasiparticles.