Study On Single Photon Transport In X-and Ladder-type Quantum Routers

Multi-channel quantum router is one of the foundations of quantum network.Multi-channel quantum routers with two CRWs coupled with multiple atoms and two CRWs coupled with Kerr nonlinear medium have been studied.In this paper,a theoretical model structured by two coupled-resonator waveguide coupled with multiple atoms is used to solve the two problems of independent control frequency and directional routing.To solve the problem of independent control frequency,we build a quantum router model consisting of a coupled-resonator waveguide with two Rydberg atoms interacting with Rydberg interaction in the central cavity.Under the control of classical light field between two excited states,a three-level atom mediated by Rydberg interaction can be regarded as a quantum emitter to route photons.It can be found that the two Rydberg interactions have different effects on the spectrum.The quantum router can route photons of two different frequencies,one of which can be turned off by controlling the Rydberg interaction and Rabi frequencies.We also find that a photon of a particular frequency can be transmitted and the frequency of the transmitted photon can be changed by adjusting the Rydberg interaction.In order to solve the problem of directional routing,the model is composed of two coupled-resonator waveguide and four single cavities,and an atom is placed at the intersection of the coupled-resonator waveguide and single cavities to form multiple node cavities.Since multiple node cavities exist in the quantum router,there are multiple pathways for photons to interfere with each other from the incident port to the outgoing port.Under the control of the phase difference between two classical light fields,the mutual interference between different pathways can be adjusted to constructive interference or destructive interference,which leads to the increase and decrease of routing probability.We found that part of the output ports can be closed under certain parameter conditions,and explore the physical mechanism of this phenomenon.The influence of Rabi frequency and coupling strength on single photon routing probability is also studied.We also find that through the interaction between different paths,it is possible to realize the directional routing from the specified port with the outgoing probability of nearly 100%.The research results of this paper provide a new theoretical scheme for multichannel quantum routers and provide valuable insights for the establishment of quantum networks.