Nonreciprocal single-photon frequency converter via multiple semi-infinite coupled-resonator waveguides

摘要

We propose to construct a nonreciprocal single-photon frequency converter viamultiple semi-infinite coupled-resonator waveguides (CRWs). We firstdemonstrate that the frequency of a single photon can be convertednonreciprocally through two CRWs, which are coupled indirectly byoptomechanical interactions with two nondegenerate mechanical modes. Based onsuch nonreciprocity, two different single-photon circulators are proposed inthe T-shaped waveguides consisting of three semi-infinite CRWs, which arecoupled in pairwise by optomechanical interactions. One circulator is proposedby using two nondegenerate mechanical modes and the other one is proposed byusing three nondegenerate mechanical modes. Nonreciprocal single-photonfrequency conversion is induced by breaking the time-reversal symmetry, and theoptimal conditions for nonreciprocal frequency conversion are obtained. Theseproposals can be used to realize nonreciprocal frequency conversion of singlephotons in any two distinctive waveguides with different frequencies and theycan allow for dynamic control of the direction of frequency conversion bytuning the phases of external driving lasers, which may have versatileapplications in hybrid quantum networks.