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arXiv:2602.06140

Highly-Indistinguishable Single-Photons at 1550 nm from a Two-photon Resonantly Excited Purcell-enhanced Quantum Dot

Robert Behrends, Martin v. Helversen, Pratim K. Saha, Lucas Rickert, Koray Kaymazlar, Mareike Lach, Nils D. Kewitz, Jochen Kaupp, Yorick Reum, Tobias Huber-Loyola, Sven Höfling, Andreas Pfenning, Tobias Heindel

cond-mat.mes-hallquant-phSubmitted Feb 5, 2026• Announced Feb 9, 2026• 2 citations
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Abstract

In this work we present a cavity-enhanced InAs/$\mathrm{In_{0.53}Al_{0.23}Ga_{0.24}As}$ quantum dot (QD) single-photon source in the telecom C-band with a record-low biexciton emitter decay time of \SI{67.4(2)}{ps} under resonant two-photon excitation (TPE). We observe strong multiphoton suppression associated with $g^{(2)}_\mathrm{X}(0) = 0.006(1)$ and $g^{(2)}_\mathrm{XX}(0) = 0.007(1)$ for the exciton (X) and biexciton (XX) emission, respectively. Due to a asymmetric Purcell enhancement of the XX-X cascade, the two-photon interference (TPI) visibility of XX photons under $π$-pulse excitation of $V_{\rm{TPI}} = 90(3)\%$ reaches the theoretical limit and clearly exceeds the $\sim60\%$ expected for standard XX-X cascades without photonic engineering. Furthermore, adding a second timed laser pulse coinciding with XX emission energy, we demonstrate stimulated TPE in the telecom C-Band. The result is an improved TPI visibility of the X photons of $V_{\rm{TPI}}=0.69(3)$ compared to TPE with $V_{\rm{TPI}}=0.61(4)$, with both being reduced compared to the theoretical values due to present dephasing effects. The advances presented in this work hold important promises for the implementation of advanced schemes of quantum communication using deterministic quantum light sources.

Comments
9 pages, 3 figures

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In this work we present a cavity-enhanced InAs/In0.53Al0.23Ga0.24As\mathrm{In_{0.53}Al_{0.23}Ga_{0.24}As}In0.53​Al0.23​Ga0.24​As quantum dot (QD) single-photon source in the telecom C-band with a record-low biexciton emitter decay time of \SI{67.4(2)}{ps} under resonant two-photon excitation (TPE). We observe strong multiphoton suppression associated with gX(2)(0)=0.006(1)g^{(2)}_\mathrm{X}(0) = 0.006(1)gX(2)​(0)=0.006(1) and gXX(2)(0)=0.007(1)g^{(2)}_\mathrm{XX}(0) = 0.007(1)gXX(2)​(0)=0.007(1) for the exciton (X) and biexciton (XX) emission, respectively. Due to a asymmetric Purcell enhancement of the XX-X cascade, the two-photon interference (TPI) visibility of XX photons under πππ-pulse excitation of VTPI=90(3)%V_{\rm{TPI}} = 90(3)\%VTPI​=90(3)% reaches the theoretical limit and clearly exceeds the ∼60%\sim60\%∼60% expected for standard XX-X cascades without photonic engineering. Furthermore, adding a second timed laser pulse coinciding with XX emission energy, we demonstrate stimulated TPE in the telecom C-Band. The result is an improved TPI visibility of the X photons of VTPI=0.69(3)V_{\rm{TPI}}=0.69(3)VTPI​=0.69(3) compared to TPE with VTPI=0.61(4)V_{\rm{TPI}}=0.61(4)VTPI​=0.61(4), with both being reduced compared to the theoretical values due to present dephasing effects. The advances presented in this work hold important promises for the implementation of advanced schemes of quantum communication using deterministic quantum light sources.
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Quantum dots are promising candidates for deterministic single-photon sources, yet achieving high photon indistinguishability at telecom wavelengths remains a critical challenge. Here, we report a quantum dot-based single-photon source operating in the telecommunications C-band that achieves a raw two-photon interference visibility of up to (91.7+-0.2)%, thus setting a new benchmark for indistinguishability in this spectral range. The device consists of an indium arsenide (InAs) quantum dot embedded within indium aluminum gallium arsenide (InAlGaAs) and integrated into a circular Bragg grating resonator. We explore multiple optical excitation schemes to optimize coherence and source performance. To our knowledge, this is the first demonstration of two-photon interference visibility exceeding 90% from a quantum-dot emitter in the telecommunications C-band, advancing the viability of solid-state sources for quantum communication and photonic networks.
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Semiconductor quantum dots (QDs) enable the generation of single and entangled photons, useful for various applications in photonic quantum technologies. Specifically for quantum communication via fiber-optical networks, operation in the telecom C-band centered around 1550 \,nm is ideal. The direct generation of QD-photons in this spectral range and with high quantum-optical quality, however, remained challenging. Here, we demonstrate the coherent on-demand generation of indistinguishable photons in the telecom C-band from single QD devices consisting of InAs/InP QD-mesa structures heterogeneously integrated with a metallic reflector on a silicon wafer. Using pulsed two-photon resonant excitation of the biexciton-exciton radiative cascade, we observe Rabi rotations up to pulse areas of 4π4π4π and a high single-photon purity in terms of g(2)(0)=0.005(1)g^{(2)}(0)=0.005(1)g(2)(0)=0.005(1) and 0.015(1)0.015(1)0.015(1) for exciton and biexciton photons, respectively. Applying two independent experimental methods, based on fitting Rabi rotations in the emission intensity and performing photon cross-correlation measurements, we consistently obtain preparation fidelities at the πππ-pulse exceeding 80%\%%. Finally, performing Hong-Ou-Mandel-type two-photon interference experiments we obtain a photon-indistinguishability of the full photon wave packet of up to 35(3)%35(3)\%35(3)%, representing a significant advancement in the photon-indistinguishability of single photons emitted directly in the telecom C-band.
Abstract Two‐photon interference from an InAs/InAlGaAs quantum dot (QD) emitting in the telecom C‐band with a raw two‐photon interference visibility of % is demonstrated. This is achieved by a two‐fold approach: an improvement of the molecular beam epitaxial growth for better QDs, and integration of the QDs into an optical circular Bragg grating resonator for a Purcell enhancement of the radiative decay rate. The quantum optical properties of the fabricated device are studied by means of time‐correlated single‐photon counting under quasi‐resonant excitation of the charged exciton line. A reduced lifetime of ps is found corresponding to a Purcell factor of F p ≧ . Pronounced anti‐bunching of the second‐order autocorrelation function at zero time delay confirms the single‐photon emission character. The two‐photon interference is demonstrated with an unbalanced Mach‐Zehnder interferometer in the Hong‐Ou‐Mandel configuration. Strategies are discussed on how to further improve the indistinguishability, and provide a survey of the state‐of‐the‐art.
Long-distance quantum communication relies on the ability to efficiently generate and prepare single photons at telecom wavelengths. In many applications these photons must also be indistinguishable such that they exhibit interference on a beamsplitter, which implements effective photon-photon interactions. However, deterministic generation of indistinguishable single photons with high brightness remains a challenging problem. We demonstrate two-photon interference at telecom wavelengths using an InAs/InP quantum dot in a nanophotonic cavity. The cavity enhances the quantum dot emission, resulting in a nearly Gaussian transverse mode profile with high out-coupling efficiency exceeding 36% after multi-photon correction. We also observe Purcell enhanced spontaneous emission rate up to 4. Using this source, we generate linearly polarized, high purity single photons at 1.3 micron wavelength and demonstrate the indistinguishable nature of the emission using a two-photon interference measurement, which exhibits indistinguishable visibilities of 18% without post-selection and 67% with post-selection. Our results provide a promising approach to generate bright, deterministic single photons at telecom wavelength for applications in quantum networking and quantum communication.