Non-Markovian decoherence dynamics of strong-coupling hybrid quantum systems: A master equation approach

Based on the experiments [S. Putz et al., Nat. Phys. 10, 720 (2014); Nat. Photonics 11, 36 (2017)] on the hybrid quantum system of a superconducting microwave cavity coupled strongly to an inhomogeneous broadening spin ensemble, we use the exact master equation theory to investigate its non-Markovian decoherence dynamics under external driving fields. In the experiments, the spin ensemble is made of negatively charged nitrogen-vacancy defects in diamond. The exact master equation theory generalizes the fluctuation-dissipation relation and depicts in details the transient non-Markovian decoherence, in which the dissipation (relaxation) and fluctuations (noise or dephasing) dynamics is well described and the non-Markovian memory effect can be well characterized. We study the physical picture of the transient non-Markovian decoherence dynamics and explore how the non-Markovian decoherence induced by the inhomogeneous broadening of the spin ensemble is suppressed in the strong-coupling regime. We also show how the spectral hole burning generates localized bound states for the further decoherence suppression. Furthermore, we investigate the two-time correlations to show the relationships between quantum fluctuations and quantum memory.