| In recent years,quantum information has developed rapidly.Quantum network is an important part of implementing quantum information processing.In an efficient optical quantum network,photons are used as ideal information carriers due to their fast propagation speeds,stable coherence and low dissipations,and quantum nodes connect different quantum channels,while quantum routers in quantum nodes control the transmission path of quantum signals.Recently,the rapid development of photon transport technology in coupled waveguide systems provides an ideal platform for single-photon quantum routing,in which the waveguide is utilized as a quantum channel for optical signal transmission,and the quantum emitter coupled to the waveguide is used to route photons to each channel.However,in the current routing system,the routing rate of the routers from the main channel to other channels is not more than 0.5,which may limit its more potential applications.A high routing rate can achieve efficient expected allocation of information between channels.Therefore,it is vital to design a quantum router with high routing rate for a multi-channel quantum network.In this paper,several efficient quantum routing schemes are provided to improve the routing rate in these systems.The main idea of these schemes is to add quantum emitters in the dual-channel or multi-channel waveguide systems.By adjusting the parameters of different emitters,efficient transfer of quantum information can be realized from the incident channel to other channels.The main content of the full text is listed as follows:(1)By locating a cyclic ?-type three-level atom in the cross cavity of an X-shaped coupled-cavity waveguide as an ideal router to connect the two channels,and placing a twolevel atom on the main channel of the waveguide to regulate the four ports,efficient quantum routing can be achieved after adjusting the atom-photon coupling strength,detuning,and the coupling between atoms and waveguides.(2)The asymmetric coupling on both sides of a cross cavity in an X-shaped coupledresonator waveguide is regulated to control photons routing.Using robust and adjustable coupling between cavities,high transfer rate between quantum channel and the output channel desired probability distribution between the two ports can be realized.Based on the coupling from a simple control circuit with additional magnetic field,the proposed scheme can effectively control the quantum routing.(3)Further,after expanding a single X-shaped waveguide to a multi-X-shaped waveguide,and placing a ?-type three-level atom two waveguide intersections to couple them,the routing rate of photons from the input channel to other channels in the system can be obtained by a discrete coordinate algorithm and a transfer matrix algorithm.Adjusting the coupling between atoms and waveguides,the efficient routing rate can be achieved to dramatically exceed o.5.(4)A new router is designed by adding a two-level atom in the cross coupled three-level system.The boundary effect of the semi-infinite long coupled-cavity waveguide is used to modify the radiation field and then increase the transmission rate.By using the discrete coordinate scattering method,the single photon scattering amplitude entering the three ports of the waveguide network is obtained,and the routing results when photons are incident from a semi-infinite or infinitely long waveguide are analyzed.These results show that the quantum routing of single photons can be controlled by adjusting the coupling strength between twolevel atom and the cavity field.(5)A single T-shaped waveguide is extended to a multiple-T-shaped waveguide,whose network channel is composed of an infinitely long coupled-resonator array and several intersecting semi-infinitely long coupled resonator arrays,and is coupled to each other by three-level atoms embedded in the crossed resonator.The single-photon transmission amplitudes of the double-and triple-T waveguide are analyzed by using the discrete coordinate scattering method.Results show that the probability of photons transferring to another channel can significantly exceed 0.5.Furthermore,the transmission amplitude of more channels can also be accurately obtained by using the transmission matrix method,so quantum routing in a scalable waveguide network can be effectively enhanced by adjusting the relevant parameters.These designs of quantum routing systems provide useful reference for the implementation of efficient optical quantum routing. |
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