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

Abstract

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 emittercavity coupling strengths and high quality factor cavities. In this regime, the broad spectrum of the dissipative quantum system is funneled into the narrow lineshape 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.Indistinguishable single photons are the building blocks of various optically-based quantum information applications such as linear optical quantum computing [1, 2], boson sampling [3][4][5][6][7], quantum teleportation [8] or quantum networks [9]. Indistinguishable photons are usually generated either using parametric down conversion [10], or alternatively directly from a single two-level quantum emitter such as atoms, color centers, quantum dots or organic molecules [11][12][13][14][15][16][17][18][19][20]. Parametric down conversion is presently the most mature technology available, but the usual low efficiency of the nonlinear processes is a severe limitation to the scalability of such sources. On the other hand, sources based on single solid-state quantum systems have been greatly developped in the last decade, as they hold the promise to combine indistinguishable, on-demand, energy-efficient, electrically drivable and scalable characteristics. However, except at cryogenics temperature, solid-state systems emitting single-photons are subject to strong pure dephasing processes [21][22][23][24][25][26][27][28][29], making them at first view inappropriate for quantum applications requiring photon indistinguishability.A two-level quantum emitter (QE) coupled only to vacuum fluctuations should emit perfectly indistinguishable photons. However, as soon as pure dephasing of the QE occurs, the degree of indistinguishability of the emitted photons is reduced to [30]where γ = 1/T 1 is the population decay rate, γ * /2 = 1/T * 2 the pure dephasing rate, and 1/T 2 = 2/T 1 + 1/T 2 * the total dephasing rate. For solid-state QE emitting photons at room temperature such as color centers, quantum dots or organic molecules, pure dephasing rates are typically several orders of magnitude larger than the population decay rate (typically ranging from 3 to 6 orders of magnitude) [12,14,21,22,24,[26][27][28][29]31]. Hence the intrinsic indistinguishability given by Eq. 1 is almost zero. A possible way to enhance the indistinguishability is to spectrally filter the emitted photons a posteriori. However, this linear-filter strategy leads to a very low efficiency. Engin...

Imaginary echoes

“…Comparing cases (ii) and (iii) above, we see that there is a formal analogy between a spectral filter and an optical cavity, as has been alluded to elsewhere 43,45 . That is not to say, however, that the two are equivalent; as a filter is reduced in width and the sideband removed, one simply moves photons from the detected channel to the out-of-plane channel.…”

“…not via the cavity mode) is given byẼ O (t) ≈ i Γ O /2πσ(t)B − (t), which takes the same form as in case (i). We make the assumption that the detected field consists of those photons emitted by the cavity mode 24,27,41,45 . Although it is customary to define the detected field in this way for QD-cavity systems, one expects that in the very broad cavity limit the detected field will also contain a contribution arising from direct QD emission.…”

Engineering a squeezed phonon reservoir with a bichromatic driving of a quantum dot

“…However, in the squeezed reservoir engineered from a phonon bath, an increase of the number of phononsn is accompanied by a decrease of the two-photon correlations |M |, as seen from Eq. (34). As a consequence, ideally squeezed reservoir atn = 0 becomes an imperfectly squeezed reservoir when n = 0.…”

“…Moreover, an interesting phenomenon of population inversions between the excitonic states of a quantum dot located inside an optical cavity and interacting with a phonon bath has been demonstrated both theoretically and experimentally [28][29][30][31][32]. The investigation of this interaction in a quantum dot-cavity system has led to the prediction of single photon sources and the realization of single-photon devices [33][34][35][36]. The influence of a phonon bath on the photon blockade effect in a driven dot-cavity system and the emission of correlated and entangled photons has also been treated [37][38][39].…”

Generating indistinguishable photons from a quantum dot in a noisy environment

“…One method is to reduce the emitter lifetime (T 1 ) so that it masks T * 2 , typically achieved with Purcell enhancement by embedding the QD in a highquality factor (Q) cavity [3,[47][48][49]. Unfortunately, increased charge noise often accompanies the Purcell enhancement in processed photonic devices [43][44][45].…”