A quantum-coherent photon--emitter interface in the original telecom band

Abstract

Quantum dots stand out as the most advanced and versatile light-matter interface available today. Their ability to deliver high-quality, high-rate, and pure photons has set benchmarks that far surpass other emitters. Yet, a critical frontier has remained elusive: achieving these exceptional capabilities at telecom wavelengths, bridging the gap to fiber-optic infrastructure and scalable silicon photonics. Overcoming this challenge demands high quality quantum materials and devices which, despite extensive efforts, have not been realized yet. Here, we demonstrate waveguide-integrated quantum dots and realize a fully quantum-coherent photon-emitter interface operating in the original telecommunication band. The quality is assessed by recording transform-limited linewidths only 8 % broader than the inverse lifetime and bright 41.7 MHz emission rate under 80 MHz $π$-pulse excitation, unlocking the full potential of quantum dots for scalable quantum networks.

Figures (4)

• Figure 1: Telecom quantum dots in a gated photonic crystal waveguide.a, Scanning electron micrograph of a photonic nanostructure with lattice constant, $a=338nm$, hosting gated telecom quantum dots. Inset: Scanning transmission electron microscope cross-section of the GaAs membrane in the QD area, showing defect-free epitaxial growth. b, Resonance fluorescence (RF) map under continuous wave excitation. The white circle at ($-355mV$, 1297.726 nm, 231.013 THz) indicates the main resonance considered.
• Figure 2: Coherent single-photon emission from telecom quantum dots.a, Resonance fluorescence of a quantum dot (neutral exciton) featuring a transform-limited linewidth. The fit is a Lorentzian with full-width half-maximum of $\Gamma_{RF}$ = $1.15(5)$ GHz. b, Time-resolved fluorescence of the emission line in A, with lifetime $\tau = 150(2)$ ps, corresponding to a Fourier-transformed-limited linewidth of $\gamma_1=1.08(1)$ GHz. A slow background, which contributes to $\sim1$% of the total count rate, with a decay time of $3.1(1)$ ns is observed, likely stemming from background emission of neighboring QDs. c, Statistical distribution of the mean linewidth of the 19 quantum dots in Fig. 1b with overall average linewidth 0.8 GHz. Insets: Additional RF scans with $\lambda=1297.640$ nm, $V_g=-369$ mV, and $0.26(1)$ GHz linewidth (top) and $\lambda=1297.665$ nm, $V_g=-350$ mV, and $0.53(4)$ GHz linewidth (bottom). d, Detected counts as a function of laser pulse power, resulting in a peak rate of 3.9 MHz into the detector at $\pi$-pulse. Inset: Rabi oscillations obtained with a narrow (1.5 GHz) etalon filter demonstrating coherent nature of the quantum emitter.
• Figure 3: State-of-the-art of telecom quantum emitters. Values of photon collection efficiency and linewidth broadening. The data is reported from a survey of the literature, where different excitation schemes are used as well as different nanostructures. The label indicates the material platform. References: $\diamond$zahidy2024quantum, $\lhd$nawrath2019coherence, $\rhd$hauser2025deterministic, $\blacksquare$joos2024coherently, $\nabla$nawrath2023bright, $\oplus$holewa2024high, $\otimes$srocka2020deterministically, $\ast$komza2024indistinguishable, $\vee$ourari2023indistinguishable. Details are given in Supplementary Table S2.
• Figure 4: Single-photon source operation.a, Raw auto-correlation measurement $g^{(2)}(\tau)$ confirming single-photon emission. Inset: Zoom around the central peak in the range $\pm5\tau$, i.e., including $99.3$ % of the collected photons. The area of the peak is normalized to that of the infinitely far-away side peaks, yielding a $g^{(2)}(0)=0.0610(2)$. b, Relative areas of side-peaks at long time-scales, showing the low-levels of blinking from a high-quality quantum emitter. c, Measurement of coincidence counts in a Hong-Ou-Mandel setup for parallel (indistinguishable) and perpendicular (fully distinguishable) configurations. d, Zoom around the central normalized peak. The raw visibility $V_\text{raw} = (83.8 \pm 0.1)$ % is calculated over a $\pm750$ ps window, corresponding to $\sim5\tau$, i.e., including $99.3$ % of the collected photons.