Dynamics and Thermalization in Many-Body Quantum Systems I

We study the entanglement dynamics of a family of quantum collision models by analytically solving the pairwise concurrence for all qubit pairs. We introduce a diagrammatic method that offers an intuitive, frame-by-frame understanding of these dynamics. This allows us to monitor how a single collision affects the entanglement of the whole many-body system. In particular, among the multiple examples we will be showing, we find a new type of genuine multipartite entanglement, called all-to-all entanglement, where every qubit is entangled with every other qubit. We find that in some models, all-to-all entangled state is hypersensitive to local excitation fluctuations: The presence of even a single excited qubit can destroy the all-to-all entanglement. We offer a detailed mathematical treatment on the phenomena, which can help us understand the disappearance of long-range entanglement in condensed matter systems above zero temperature. We also speculate a possible property of all-to-all entangled state: Every subsystem of it is entangled with every other subsystem.