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