Tunable targeted single-photon routing in a waveguide-QED structure containing a time-modulated two-level atom

Abstract

Single-photon routing between two one-dimensional waveguides mediated by a single-mode cavity embedded with a time-modulated two-level atom is investigated. Two configurations, where the single photon is incident from an infinite or semi-infinite waveguide, are considered. Using the analytical expressions of the single-photon scattering amplitudes, the transmission behaviors in the two waveguides are discussed. The results show that the time modulation of the atomic frequency enables a dynamically tunable quantum router. A single photon with different frequencies can be routed dynamically from the incident waveguide to the other by properly manipulating the amplitude-to-frequency ratio of the atom. The routing efficiency can be improved to approach 100% by terminating the incident waveguide. In the semi-waveguide configuration, the routing behaviors controlled by the quantum coherent feedback are also investigated. The influence of the phase shifts introduced by the terminated waveguide on the routing capability and the conditions for perfect single-photon routing are discussed in detail. A frequency tunable targeted single-photon router can even be realized with the help of chiral coupling. These results may be beneficial to the photon control in a quantum network based on time-modulated quantum nodes.