Single-photon nonreciprocal transport in one-dimensional coupled-resonator waveguides

We study the transport of a single photon in two coupled one-dimensional\nsemi-infinite coupled-resonator waveguides (CRWs), in which both end sides are\ncoupled to a dissipative cavity. We demonstrate that a single photon can\ntransfer from one semi-infinite CRW to the other nonreciprocally. Based on such\nnonreciprocity, we further construct a three-port single-photon circulator by a\nT-shaped waveguide, in which three semi-infinite CRWs are pairwise mutually\ncoupled to each other. The single-photon nonreciprocal transport is induced by\nthe breaking of the time-reversal symmetry and the optimal conditions for these\nphenomena are obtained analytically. The CRWs with broken time-reversal\nsymmetry will open up a kind of quantum devices with versatile applications in\nquantum networks.\n