Non-Markovianity in experimentally simulated quantum channels: Role of counterrotating-wave terms

We experimentally investigate the non-Markovianity problems in a quantum channel implemented by an all-optical setup. The quantum channel simulates the dynamics of a two-level (qubit) system surrounded by bosonic modes, with the system-environment interaction treated without applying the rotating-wave approximation (RWA). Therefore, it allows us to demonstrate the important role of counterrotating-wave terms in influencing the memory effects of the environment. The experimental and theoretical results are in good agreement and show quite different behaviors of the non-Markovianity measure between RWA and non-RWA channels. One can find the nonmonotonic dependence of the non-Markovianity measure on the coupling and detuning parameters in the non-RWA case, which is attributed to the competing mechanisms caused by the counterrotating-wave terms. We emphasize that the non-RWA channel provides a more clear description of the open-system dynamics and the counterrotating-wave terms are indispensable in the study of non-Markovianity.