Path-integral approach for nonequilibrium multitime correlation functions of open quantum systems coupled to Markovian and non-Markovian environments
M. Cosacchi, Moritz Cygorek, F. Ungar, A. M. Barth, Alexei Vagov, V. M. Axt · Physical review. B./Physical review. B · 2018
The memory induced by the environment is of utmost importance for many few-level quantum systems in condensed matter. Here, the authors show how a real-time path-integral approach can be used to calculate nonequilibrium multitime correlation functions of open few-level quantum systems without any approximation to the model, dealing consistently with non-Markovian and Markovian reservoirs. This method avoids using the quantum regression theorem that is not valid when memory matters. The authors illustrate the new scheme by calculating the emission spectrum of a quantum dot and the second-order photonic two-time correlation function of a quantum dot-cavity system.