Arnd Bäcker – Entanglement generation in coupled chaotic systems
When combining two quantum systems with known properties, what are the properties of the resulting bipartite system in dependence on the amount of coupling between the subsystems? Here we concentrate on how much entanglement is generated (a) in the eigenstates and (b) by the time-evolution of states which are initially product states. The answer depends on properties of the subsystems, the amount of coupling and the type of initial states. For the case that both systems are quantum chaotic a universal description of the perturbative regime of small coupling is obtained for the eigenstate entanglement which can be extended to the regime of strong coupling. For the entanglement dynamics an additional re-scaling of time also establishes a universal description. These results are illustrated for coupled maps with classically chaotic dynamics and for quantum chaotic spin chains. If one of the subsystems is integrable, while the other is chaotic, a modified transition parameter becomes relevant.