Memory loss is contagious in open quantum systems

Memoryless (Markovian) system-bath interactions are of fundamental interest in physics. While typically the absence of memory originates from the characteristics of the bath, here we demonstrate that it can result from the system becoming lossy due to the Markovian interaction with a second bath. This suggests that the property of Markovianity is “contagious”, i.e., it can be transferred from one bath to another through the system with which they both interact. We introduce a Bloch-Redfield-inspired approach that assumes a Markovian interaction due to the system losses and significantly improves the description of the bath-driven population transfer in a lossy system coupled to a non-Markovian bath. Furthermore, it indicates that such interactions are well-described by an effective spectral density that takes into account the broadening of the system's energy levels due to dissipation. Our findings reduce the computational demand in the theoretical description of complex system-bath setups and pave the way for further studies of counterintuitive Markovian interactions.