Bright solid-state sources of indistinguishable single photons

Abstract

Bright sources of indistinguishable single photons are strongly needed for the scalability of quantum information processing. Semiconductor quantum dots are promising systems to build such sources. Several works demonstrated emission of indistinguishable photons while others proposed various approaches to efficiently collect them. Here we combine both properties and report on the fabrication of ultrabright sources of indistinguishable single photons, thanks to deterministic positioning of single quantum dots in well-designed pillar cavities. Brightness as high as 0.79±0.08 collected photon per pulse is demonstrated. The indistinguishability of the photons is investigated as a function of the source brightness and the excitation conditions. We show that a two-laser excitation scheme allows reducing the fluctuations of the quantum dot electrostatic environment under high pumping conditions. With this method, we obtain 82 ± 10% indistinguishability for a brightness as large as 0.65 ± 0.06 collected photon per pulse.

Photoneutralization and slow capture of carriers in quantum dots probed by resonant excitation spectroscopy

“…However, this issue is overcome with the use of an additional weak non-resonant laser which neutralizes the QD and optically gates its RE [24], as also shown in other recent experimental studies [25,28,29]. The use of an additional weak non-resonant laser also appears to be interesting to probe the local environment fluctuations at the single-charge level in single QD [30] and to minimize this environment fluctuations to improve the emitted photons indistinguishability [31].…”

Two-Photon Interference from the Far-Field Emission of Chip-Integrated Cavity-Coupled Emitters

“…We could significantly reduce this effect by using resonant pumping [15][16][17] or quasi-resonant pumping 41,42 The temperature tuning method we employ also provides only a limited tuning range because the linewidth of the quantum dots broadens with increasing temperature, which will ultimately degrade the two-photon interference contrast. 14 Future devices could incorporate DC Stark shift 20 or local strain tuning 43 to enable wider tuning ranges.…”

Two-photon interference from a quantum dot microcavity: Persistent pure dephasing and suppression of time jitter

“…In the regime of cQED, the lifetime of the QD excitons can be manipulated via the photonic density of states in the cavity (the Purcell effect). If the timing of emission events is precisely known, and γ is constant, shortening of the emitter lifetime T 1 via the Purcell effect leads to an improved interference visibility as the condition T 2 = 2T 1 can be approximately restored [7,17,25]. This simple picture, however, is known to break down if there are uncertainties in the timing of emission events (time jitters) [26][27][28] or if the dephasing environment gives rise to more than a simple constant pure-dephasing rate, as is known to be the case for phonons [28][29][30][31][32].…”

“…When embedded in a bulk semiconductor, however, QDs suffer from poor photon extraction efficiencies, since only a minor fraction of the photons can leave the high refractive index material. This problem can be mitigated by integrating QDs into optical microcavities [12,[16][17][18] or photonic waveguides [19][20][21], which can enhance extraction efficiencies to values beyond 50%.…”