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arXiv:2501.15970 · Advanced Quantum Technologies

Two‐Photon Interference from an InAs Quantum Dot Emitting in the Telecom C‐Band

Jaewon Kim, Jochen Kaupp, Yorick Reum, Giora Peniakov, Johannes Michl, Felix Kohr, Monika Emmerling, Martin Kamp, Yong‐Hoon Cho, Tobias Huber, Sven Höfling, Andreas Theo Pfenning

Published Jul 20, 2025• 14 citations
arXivHTMLPDF

Abstract

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.

DOI
10.1002/qute.202500069

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•Jan 1, 2026•0 citations
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.
The ability of individual photonic qubits to interact via interference lies at the heart of many quantum networking applications. For their development, sources of highly coherent, indistinguishable photons are therefore crucial. Here, we investigate the noise sources that affect InAs/InP quantum dots and limit their coherence. We show that the droplet epitaxy growth mode leads to a quiet environment with 96% of exciton transitions having a coherence time above 100 ps, even under non-resonant excitation. Further, Hong–Ou–Mandel interference reveal a corrected two-photon interference visibility of 98.6±1.6% for these quantum dots, showing their potential for quantum networking applications.
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.
In this study, we investigate as-grown InAsP/InP quantum dots emitting in the third telecommunication window under detuned quasi-resonant excitation. A large excitation-emission detuning of 32 meV enables efficient suppression of scattered laser light while retaining several advantages of near-resonant excitation. The single-photon nature of the emission is confirmed by a Hanbury Brown and Twiss experiment, yielding a raw second-order autocorrelation value of graw(2)(0)=0.076(6)g_{\mathrm{raw}}^{(2)}(0)=0.076(6)graw(2)​(0)=0.076(6). Hong-Ou-Mandel measurement is used to determine the degree of indistinguishability of single photons and reveal as measured visibilities of V=0.094(4)V=0.094(4)V=0.094(4) and V=0.106(5)V=0.106(5)V=0.106(5) for excitation pulse separations of 13.1 ns and 5.3 ns, respectively. These results demonstrate the potential of as-grown InAsP/InP quantum dots grown via molecular beam epitaxy under not experimentally demanding detuned excitation for generating indistinguishable telecom single photons. Further improvements are to be achieved through Purcell enhancement in optical cavities.
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. The demonstration of two-photon interference visibilities exceeding 90% from a quantum-dot emitter in the telecommunications C-band pushes solid-state single-photon sources further towards practical quantum communication and quantum networks.
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.
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. The demonstration of two-photon interference visibilities exceeding 90% from a quantum-dot emitter in the telecommunications C-band pushes solid-state single-photon sources further towards practical quantum communication and quantum networks.