A Case Study of Quantum Non-Markovianity: 1D Photon Scattered from a Qubit in Front of a Mirror

We propose a model system for the study of quantum non-Markovian (NM) physics. We consider a single-photon wavepacket scattered off a single two-level system strongly coupled to a one-dimensional waveguide terminated by a perfect mirror, and apply the tools of open quantum systems to investigate the NM memory effects in the scattering dynamics. By finding the exact, time-dependent solutions in both the one- and two-excitation sectors, we explicitly construct the qubit's dynamical map (DM), based on which various NM measures can be applied. For instance, the geometric measure proposed by Lorenzo, Plastina and Paternostro shows that for this system both the wavepacket width and the qubit-mirror separation contribute to the non-Markovianity. Our "scattering DM" is different from that for spontaneous emission in that the determinant of our DM can become negative. This suggests interesting features that call for further study of scattering setups. Ref: arXiv:1707.05946