Nonequilibrium dynamical processes are central in many quantum technological contexts. However, it has remained a key challenge to identify concepts for their characterization and classification, as the resulting quantum states purposely defy a description in terms of equilibrium statistical physics in order to realize states not accessible by conventional means. Scientists have now achieved a characterization in terms of a dynamical topological order parameter for quantum walks, which represent a paradigmatic class of nonequilibrium processes.
Source:
https://phys.org/news/2020-02-dynamical-topological-parameter-quantum.html