Cavity-Funneled Generation of Indistinguishable Single Photons from Strongly Dissipative Quantum Emitters

We investigate theoretically the generation of indistinguishable single photons from a strongly dissipative quantum system placed inside an optical cavity. The degree of indistinguishability of photons emitted by the cavity is calculated as a function of the emitter-cavity coupling strength and the cavity linewidth. For a quantum emitter subject to strong pure dephasing, our calculations reveal that an unconventional regime of high indistinguishability can be reached for moderate emitter-cavity coupling strengths and high-quality factor cavities. In this regime, the broad spectrum of the dissipative quantum system is funneled into the narrow line shape of the cavity. The associated efficiency is found to greatly surpass spectral filtering effects. Our findings open the path towards on-chip scalable indistinguishable-photon-emitting devices operating at room temperature.

Figure 1

Schematic of the system under study: a dissipative two-level emitter coupled to an optical-cavity mode.

Figure 2

(a) Indistinguishability figure of merit ($I$), (b) efficiency $\beta$, and (c) funneling ratio $\mathcal{F}$, plotted as a function of the cavity linewidth $\kappa /\gamma$ and the emitter-cavity coupling strength $g/\gamma$ for a fixed ratio ${\gamma }^{*}/\gamma ={10}^4$. The funneling ratio is defined as $\mathcal{F}=\beta I{\gamma }^{*}/\gamma$. Solid lines delimit three different regimes discussed in the text: coherent coupling (“1”), incoherent coupling and bad-cavity regime (“2”), and incoherent coupling and good-cavity regime (“3”).

Figure 3

Indistinguishability figure of merit $I$ (full calculation in black solid line), efficiency $\beta$ (blue solid line), and cavity-funneling ratio $\mathcal{F}$ (red solid line) for a fixed emitter-cavity coupling of $g=10\gamma$. The full calculation for indistinguishability is compared with analytic expressions in two different limiting cases: incoherently coupled good-cavity regime [dotted line, Eq. (10)] and coherently coupled bad-cavity regime [dashed line, Eq. (8)]. The analytical expression for $\beta$ [dotted line, Eq. (12)] overlaps perfectly with the full calculation.