Quantum Router Modulated By Two Rydberg Atomsin A X-shaped Coupled Cavity Array

In recent years,many quantum optical devices at the single photon level have been born with the rapid development of quantum networks,especially in quantum routers.As one of the core components of quantum network,many scientific researchers put forward models and schemes in theory and experiment to realize quantum router.Coupled cavity array composed of a group of low loss cavities has become a very important experimental platform for studying the interaction between light and matter in quantum optics because of its advantages such as large buffer time and large storage capacity.In addition,Rydberg atom has gradually played an important role in the field of quantum information due to its great dipole-dipole interaction,large geometric size,large polarizability and long radiation lifetime.Therefore,we mainly use Rydberg atom and coupled-cavity array to study the scattering characteristics of single photon,so as to propose a feasible quantum router scheme.The theoretical model in this paper is an X-type coupled cavity array composed of two one-dimensional coupled cavity arrays,in which two Rydberg atoms are placed in the central cavity as a emitter.The transmission characteristics of single photon are adjusted by changing the parameters.The reflectivity,transmittance and transfer rate of the incident single photon are solved analytically by using the discrete coordinate scattering method.The coherent control of single photon scattering by parameters such as the existence of classical light field the intensity of Rydberg interaction and the intensity of the coupling between cavity and atom are studied.The results show that the Rydberg interaction has the effect of an energy level shift,and the transfer rate line summit in the scattering spectrum moves accordingly.When the Rydberg interaction is positive,it shortens the distance between the two peaks of the total transfer rate,while when the Rydberg interaction is negative,it is just the opposite.And when the Rydberg interaction is within a certain range,the summit of the transfer rate increases to three,indicating that three photons of different frequencies are absorbed by the system and scattered to each channel,thus achieving the purpose of quantum routing.This provides a feasible idea for multi-frequency photon router.The coupling strength between cavity and atom will change the peak of transmission spectrum and make it smooth.When a particular value is taken,photons within a certain bandwidth range will be transmitted to the right side of the coupling cavity array.When the energy bands of two coupled cavity arrays do not overlap at all,the phenomenon of total reflection will appear due to the bound state.It is important to note that the energy corresponding to the bound state of the resulting total reflection is not the same as that corresponding to the excited state of the system.But the appearance of bound states is related to the excited states of the system.The system has several excited states,which correspond to several bound states when the energy bands of two coupling cavity arrays do not overlap at all.In our model,the system will have at most three excited states.By adjusting the parameters,the total reflection of photons of three different frequencies can be obtained.It plays a certain role in regulating photon routing.Finally,we analyze the effect of the environment on the single photon scattering,and treat the dissipation as a constant by using the quasi-boson method.The results show that the cavity dissipation significantly reduces the peak value of the transfer spectrum and the peak value of the total transmission spectrum,which has an asymmetric effect on the peak value of the total reflection spectrum.