Distinguishing quantumness and classicality lies at the heart of quantum physics research. For example, the quantumness of a state is indicated by the negativity of the Wigner function or Glauber-Sudarshan P-function, where coherent states serve as the classical strategy to resemble a state. In an open quantum system, the system may couple to an unknown environment, such that the only information one can extract is the system dynamics. In this case, how can one tell if the system is “quantum correlated” with the environment or not? To address this, they show that a persistently classical bipartite correlation necessarily leads to a Hamiltonian ensemble simulation for the reduced system dynamics and, consequently, the nonexistence of such simulation witnesses the quantumness of the dynamics.
Figure Caption:
a) Schematic illustration showing the averaged state ¯ρ(t) resulting from the Hamiltonian ensemble {(pj,^Hj)}. (b) If a quantum system interacts with a bath, their interaction will, in general, correlate them. As we show, the nature of these correlations, i.e., classical or quantum, is intimately connected to the (im)possibility to simulate the dynamics of the open system with a Hamiltonian ensemble.
Reference
Simulating Open Quantum Systems with Hamiltonian Ensembles and the Nonclassicality of the Dynamics, Hong-Bin Chen*, Clemens Gneiting, Ping-Yuan Lo, Yueh-Nan Chen*, and Franco Nori, Phys. Rev. Lett. 120, 030403 (2018)
