Nonreciprocal single-photon router in quantum networks

High-efficiency single-photon routing of photon signals between different quantum channels is of great importance for the quantum networks with the ability to coherently transfer quantum states between the desired sender and receiver nodes. We proposed an efficient scheme for realizing quantum routers via multiple semi-infinite coupled-resonator waveguides (CRWs) coupled to cavities nonreciprocally. Numerical results show that with the change of the phase difference value, the quantum routing function of multiple output ports can be realized, in the meantime, the information conversion rate can almost reach 100%. The optimal conditions for these phenomena are obtained by the time-reversal symmetry breaking the nonreciprocal of the single-photon transport. Moreover, we have also described a scalable scheme that can extend the router to an arbitrary number of outputs. Our results pave the way to design high-quality quantum devices based on breaking time-reversal symmetry waveguide-cavity systems. (paper)