A quantum emitter coupled to an optical bimodal cavity in the solid-state implementation has recently proven to be an excellent platform for coherent generation of nonclassical light on a chip. However, the impacts of the structural couplings between the photonic modes via different arrangements of optical cavity and waveguide are rarely considered. Here, we explore in detail the characteristics of the photon antibunching in bimodal cavity quantum electrodynamics (QED) via taking into account two different cavity-waveguide arrangements: (i) an inline geometry and (ii) a side-coupled geometry. In our scheme, both cavity modes are simultaneously coupled to a two-level emitter but are not directly coupled to each other, owing to their orthogonal polarizations. It is clearly shown that the quality of the photon antibunching in the bimodal cavity QED, namely, the smallness of the second-order intensity correlation function at zero time, is closely related to the cavity-waveguide arrangements. The optimal photon antibunching can be achieved in the side-coupled geometry and the antibunching quality is about two orders of magnitude lower than that in the inline geometry. This enhancement of the photon antibunching is ascribed to the combination of two kinds of quantum interference effects in the waveguide-cavity QED system. We also find that the side-coupled architecture can make the device robust against the frequency mismatch between the two cavity modes, as compared to the inline geometry. In addition, we find that this mismatch can be used to generate better antibunching. The realization of our proposal with existing cavity-waveguide QED architectures is also discussed.1 MoreReceived 15 September 2018DOI:https://doi.org/10.1103/PhysRevA.98.053801©2018 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCavity quantum electrodynamicsQuantum description of light-matter interactionQuantum interference effectsTechniquesCavity resonatorsAtomic, Molecular & Optical
We have studied the space-time entangled Stokes-anti-Stokes photons generated from a three-level system. In the presence of counterpropagating pump and control lasers, paired Stokes and anti-Stokes fields are spontaneously emitted into opposite directions. The two-photon wave packet is generally a convolution of the phase matching and the third-order nonlinear susceptibility and the feature of the joint temporal correlation is determined by either of them. When the phase matching plays a major role in determining the spectral width of biphotons, the two-photon interference exhibits as conventional type-II spontaneous parametric down-conversion (SPDC). However, if the spectral width of paired photons is determined by the third-order nonlinear susceptibility, two types of four-wave mixings (FWMs) destructively interfere and contribute to the two-photon coincidences. In such a case, the coincidence counting rate appears as a damped Rabi oscillation and exhibits the photon antibunching. The oscillation frequency is equal to the effective Rabi frequency. We have also discussed polarization-entanglement generation in a three-state case. It is found that if the phase matching is crucial in determining the properties of paired Stokes and anti-Stokes photons, the generated state is the same as the degenerate type-II SPDC. However, if the spectral width is mainly controlled by the resonant linewidths in the third-order nonlinearity, one can select one FWM to produce polarization-entangled biphotons, but paired photons from the other FWM process is nonpolarization entangled.
Photon antibunching based on a single two-level atom strongly coupled to a single-mode optical cavity has been demonstrated in experiments. Here, we put forward an improved version of such an antibunching by introducing a pump field and a microwave field in the coupled atom-cavity system to form both a three-level $\mathrm{\ensuremath{\Delta}}$-type transition and closed-loop coupling. Via calculating the zero-time-delay second-order correlation function
g(2)(0) of the single-mode cavity field, we find that a complete photon blockade, namely,
g(2)(0)=0, can be well achieved without detuning the driving and cavity resonance. In addition, it is clearly shown that this strong photon antibunching effect appears in the weak-coupling regime of light-atom interactions. The enhanced photon antibunching is ascribed to quantum interference between the two transition paths from the three-level $\mathrm{\ensuremath{\Delta}}$ atom weakly coupled to the three involved fields (cavity, pump, and microwave). Our proposal is useful for the single-photon generation by photon blockade, which has applications in quantum information processing.