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We analyze the transport property of a single photon in a one-dimensional coupled resonator waveguide coupled with a Λ-type emitter assisted by an additional cavity. The reflection and transmission coefficients of the inserted photon are obtained by the stationary theory. It is shown that the polarization state of the inserted photon can be converted with high efficiency. This study may inspire single-photon devices for scalable quantum memory.
Realization of a quantum network requires accurate coherent control of single photons, since they play the role of a ‘flying qubit’ to transfer quantum information between different nodes in the quantum network.[1] A variety of methods are proposed for the realization of quantum control of single photons.[2,3] Among them, scattering of single photons in a one-dimensional waveguide or coupled resonator waveguide (CRW) is one of the most promising candidates.[4–20] In particular, to realize single photon quantum switching, Sun et al. used a two-level atom coupled to a one-dimensional (1D) coupled resonator waveguide to control the coherent transport of a single photon.[21] They also realized a single-photon quantum switch in cross-resonator arrays with a Λ-type atom which is localized in the intersectional resonator using the Fano–Feshbach effect based on the dark state of the Λ-type atom.[22] The single-photon routing scheme was proposed using a Δ-type Three-level atom embedded in quantum multichannels composed of a CRW or using a single atom with an inversion center coupled to quantum multichannels made of a CRW.[23,24] Controllable single-photon frequency converter was realized using a three-level V-type atom with a classical driving field.[25]
In this article, we theoretically analyze the transport property of a single photon in a 1D CRW with a Λ-type emitter assisted by an additional cavity. There are two kinds of polarization modes in the CRW. Each polarization mode is coupled to one transition of the Λ-type emitter, such that the emitter can absorb one kind of polarization photon and re-emit it with the same or different polarization. Assisted by an additional cavity, we show that the photon will be converted from one polarization to the other when it is scattered by a Λ-type emitter. This result has potential applications in scalable quantum memory.
We consider a CRW with a Λ-type emitter embedded in one of the resonators. For convenience, we assume that the emitter is located in the n-th resonator. An assisted cavity is coupled with the 0-th resonator. The hopping between the neighbor cavity is evanescent field coupling,[4–6] as shown in Fig.
Under the rotating wave approximation, the Hamiltonian for our model is
Assuming that a photon comes from the left with h polarization and the emitter is in state
We use the eigenequation
We can get transmissivity
Next, we show a potential application of our model for scalable quantum memory. As shown in Fig.
We have studied the transport property of a single photon scattering off a Λ-type emitter in a 1D CRW. We find that, assisted by an empty cavity, the photon polarization can be converted with high efficiency approaching unity when n is odd and the photon is resonated to the emitter. Our work may inspire new optical devices for scalable quantum memory.
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