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

Nature Nanotechnology (2026)Cite this article

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Abstract

Quantum dots have set benchmarks that far surpass other quantum emitters owing to their ability to deliver high-quality, high-rate and pure photons. However, achieving these exceptional capabilities at telecom wavelengths, bridging the gap to fibre-optic infrastructure and scalable silicon photonics, remains a challenge. Overcoming this difficulty demands high-quality quantum materials and devices that, despite extensive efforts, have not yet been realized. Here we demonstrate waveguide-integrated InAs quantum dots and realize a fully quantum-coherent photon–emitter interface operating in the original telecommunication band (or O-band, 1,260–1,360 nm). We record transform-limited linewidths only 8% broader than the inverse lifetime and bright 41.7-MHz emission rate under 80-MHz π-pulse excitation. These findings showcase the potential of quantum dots for scalable quantum networks.

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Fig. 1: Telecom QDs in a gated photonic crystal waveguide.
The alternative text for this image may have been generated using AI.
Fig. 2: Coherent single-photon emission from telecom QDs.
The alternative text for this image may have been generated using AI.
Fig. 3: State of the art of telecom quantum emitters.
The alternative text for this image may have been generated using AI.
Fig. 4: Single-photon source operation.
The alternative text for this image may have been generated using AI.

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Data availability

The data that support the findings of this study are presented in the article and its Supplementary Information in graphical form. The raw data and analysis scripts that support the findings of this study have been deposited in ERDA (University of Copenhagen Research Data Archive) and are available at https://doi.org/10.17894/ucph.bea2b48f-8c09-40f1-b867-aeb4a87958b8 (ref. 66), as well as from the authors upon reasonable request. The sample used is piece A3W, cleaved from wafer B15835.

Code availability

The code used to process the data and generate the figures in this study is available at https://doi.org/10.17894/ucph.bea2b48f-8c09-40f1-b867-aeb4a87958b8 (ref. 66), as well as from the authors upon reasonable request.

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Acknowledgements

We acknowledge R. A. Thomas for valuable discussions on the experimental methods. We thank A. Vogel of the Nano Imaging Lab of the Swiss Nanoscience Institute, University of Basel, for expert assistance in performing the transmission electron microscopy measurements. M.A. was funded by European Union’s Digital Europe programme (EuroQCI) under grant agreement no. 101091659. S.K., N.S. and A.L. acknowledge BMFTR-funded projects QTRAIN no. 13N17328, EQSOTIC no. 16KIS2061 and QR.N no. 16KIS2200, and the DFG-funded project EXC ML4Q LU 2004/1. Z.L. and P.L. acknowledge financial support from the Novo Nordisk Foundation (Challenge project ‘Solid-Q’). Y.M., P.L. and L.M. acknowledge financial support from the Danish National Research Foundation (Center of Excellence ‘Hy-Q,’ grant no. DNRF139). L.L.N., B.F.S. and R.J.W. were funded by the Swiss National Science Foundation via projects 20QU-1_215955 and 200021L-236481. L.M. was funded by European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant no. 949043, NANOMEQ).

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Author notes

  1. These authors contributed equally: Marcus Albrechtsen, Severin Krüger.

Authors and Affiliations

  1. Center for Hybrid Quantum Networks (Hy-Q), Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark

    Marcus Albrechtsen, Zhe Liu, Yu Meng, Peter Lodahl & Leonardo Midolo

  2. Experimental Physics VI, Faculty of Physics and Astronomy, Ruhr-Universität Bochum, Bochum, Germany

    Severin Krüger, Nikolai Spitzer & Arne Ludwig

  3. Sparrow Quantum ApS, Frederiksberg, Denmark

    Juan C. Loredo, Lucio Stefan & Peter Lodahl

  4. Department of Physics, University of Basel, Basel, Switzerland

    Lukas L. Niekamp, Bianca F. Seyschab & Richard J. Warburton

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  1. Marcus Albrechtsen
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Contributions

M.A., S.K., Y.M. and L.M. designed and built the experimental set-up and devices. Z.L. and M.A. fabricated the sample. M.A., J.C.L. and L.S. performed the optical spectroscopy measurements. M.A. and L.M. carried out the data analysis. L.L.N. and B.F.S. carried out the transmission electron microscopy analysis. S.K., N.S. and A.L. developed the growth protocol and performed the growth of QD samples. P.L., A.L., R.J.W. and L.M. conceptualized the idea of the O-band sample growth, the experiment and data analysis and provided financial support for the project. M.A. and L.M. wrote the paper with contributions from all authors.

Corresponding authors

Correspondence to Marcus Albrechtsen or Leonardo Midolo.

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Competing interests

P.L. is founder and chief quantum officer of Sparrow Quantum. The other authors declare no competing interests.

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Nature Nanotechnology thanks Marcin Syperek and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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Supplementary Figs. 1–11, Tables 1–3 and References.

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Albrechtsen, M., Krüger, S., Loredo, J.C. et al. A quantum-coherent photon–emitter interface in the original telecom band. Nat. Nanotechnol. (2026). https://doi.org/10.1038/s41565-026-02156-7

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