Sorting Out Quantum Chaos

Figure 1: Artistic rendition of a many-body open quantum system, made up of many quantum units (represented as spins) that interact among themselves and with the surrounding environment (orange lines and lightning represent, respectively, mutual interactions and coupling to the environment). If the system is forgetful, or Markovian, its dynamics can be described by a Lindbladian “superoperator.” Kawabata and colleagues showed that all possible Lindbladians can be classified in 38 groups based on symmetry. Credit: A. del Campo/University of Luxembourg further increasing the number of states to consider. As a result, open, many-body quantum systems remain a frontier of exploration in physics, for which researchers haven’t developed a systematic theoretical framework. A new study by Kohei Kawabata of Princeton University and colleagues has taken an important step toward developing such a general framework by offering a complete classification of these systems based on symmetry principles [1] (Fig. 1). The classification will help researchers chart the territory of possible phenomena that might emerge in a vast range of open, many-body systems, including those that might display “quantum chaos.”