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Joos, Raphael

Raphael Joos

Herr MSc.

PhD-Student
Institut für Halbleiteroptik und Funktionelle Grenzflächen
Semiconductor Optics Group

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+49 711 685 65227
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Allmandring 3
70569 Stuttgart
Deutschland
Raum: 1.009

Publikationen

2025
1. Pfister, U., Wendland, D., Hornung, F., Engel, L., Hüging, H., Herzog, E., Vijayan, P., Joos, R., Jung, E., Jetter, M., Portalupi, S. L., Pernice, W. H. P., & Michler, P. (2025). Telecom wavelength quantum dots interfaced with silicon-nitride circuits via photonic wire bonding. Npj Nanophotonics, 2, Article 1. https://doi.org/10.1038/s44310-025-00061-w
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  @article{Pfister2025, abstract = {Photonic integrated circuits find applications in classical and quantum communication, computing and sensing. For ideal performance, efforts are made to effectively combine different platforms to benefit from their respective strengths. Here, direct laser written photonic wire bonds are employed to interface triggered sources of quantum light, based on semiconductor quantum dots embedded into etched microlenses, with low-loss silicon-nitride photonics. Single photons at telecom wavelengths are generated by In(Ga)As quantum dots which are then funneled into a silicon-nitride chip containing single-mode waveguides and beamsplitters. The second-order correlation function of g(2)(0) = 0.11 {\textpm} 0.02, measured via the on-chip beamsplitter, clearly demonstrates the transfer of single photons into the silicon-nitride platform. The photonic wire bonds funnel on average 27.9 {\textpm} 8.0{\%} of the bare microlens emission (NA = 0.6) into the silicon-nitride-based photonic integrated circuit even at cryogenic temperatures. This opens the route for the effective future up-scaling of circuitry complexity based on the use of multiple different platforms.}, author = {Pfister, Ulrich and Wendland, Daniel and Hornung, Florian and Engel, Lena and H{\"u}ging, Hendrik and Herzog, Elias and Vijayan, Ponraj and Joos, Raphael and Jung, Erik and Jetter, Michael and Portalupi, Simone L. and Pernice, Wolfram H. P. and Michler, Peter}, day = 17, doi = {10.1038/s44310-025-00061-w}, issn = {2948-216X}, journal = {npj Nanophotonics}, month = {03}, number = 1, pages = 11, title = {Telecom wavelength quantum dots interfaced with silicon-nitride circuits via photonic wire bonding}, url = {https://doi.org/10.1038/s44310-025-00061-w}, volume = 2, year = 2025 }
  Link
  https://doi.org/10.1038/s44310-025-00061-w
2024
1. Corcione, E., Jakob, F., Wagner, L., Joos, R., Bisquerra, A., Schmidt, M., Wieck, A. D., Ludwig, A., Jetter, M., Portalupi, S. L., Michler, P., & Tarín, C. (2024). Machine learning enhanced evaluation of semiconductor quantum dots. Scientific Reports, 14, Article 1. https://doi.org/10.1038/s41598-024-54615-7
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  @article{Corcione2024, abstract = {A key challenge in quantum photonics today is the efficient and on-demand generation of high-quality single photons and entangled photon pairs. In this regard, one of the most promising types of emitters are semiconductor quantum dots, fluorescent nanostructures also described as artificial atoms. The main technological challenge in upscaling to an industrial level is the typically random spatial and spectral distribution in their growth. Furthermore, depending on the intended application, different requirements are imposed on a quantum dot, which are reflected in its spectral properties. Given that an in-depth suitability analysis is lengthy and costly, it is common practice to pre-select promising candidate quantum dots using their emission spectrum. Currently, this is done by hand. Therefore, to automate and expedite this process, in this paper, we propose a data-driven machine-learning-based method of evaluating the applicability of a semiconductor quantum dot as single photon source. For this, first, a minimally redundant, but maximally relevant feature representation for quantum dot emission spectra is derived by combining conventional spectral analysis with an autoencoding convolutional neural network. The obtained feature vector is subsequently used as input to a neural network regression model, which is specifically designed to not only return a rating score, gauging the technical suitability of a quantum dot, but also a measure of confidence for its evaluation. For training and testing, a large dataset of self-assembled InAs/GaAs semiconductor quantum dot emission spectra is used, partially labelled by a team of experts in the field. Overall, highly convincing results are achieved, as quantum dots are reliably evaluated correctly. Note, that the presented methodology can account for different spectral requirements and is applicable regardless of the underlying photonic structure, fabrication method and material composition. We therefore consider it the first step towards a fully integrated evaluation framework for quantum dots, proving the use of machine learning beneficial in the advancement of future quantum technologies.}, author = {Corcione, Emilio and Jakob, Fabian and Wagner, Lukas and Joos, Raphael and Bisquerra, Andre and Schmidt, Marcel and Wieck, Andreas D. and Ludwig, Arne and Jetter, Michael and Portalupi, Simone L. and Michler, Peter and Tar{\'i}n, Cristina}, day = 20, doi = {10.1038/s41598-024-54615-7}, issn = {2045-2322}, journal = {Scientific Reports}, month = {02}, number = 1, pages = 4154, title = {Machine learning enhanced evaluation of semiconductor quantum dots}, url = {https://doi.org/10.1038/s41598-024-54615-7}, volume = 14, year = 2024 }
  Link
  https://doi.org/10.1038/s41598-024-54615-7
2. Vijayan, P., Joos, R., Werner, M., Hirlinger-Alexander, J., Seibold, M., Vollmer, S., Sittig, R., Bauer, S., Braun, F., Portalupi, S., Jetter, M., & Michler, P. (2024). Growth of telecom C-band In(Ga)As quantum dots for silicon quantum photonics. Materials for Quantum Technology, 4. https://doi.org/10.1088/2633-4356/ad2522
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  @article{article, author = {Vijayan, Ponraj and Joos, Raphael and Werner, Marco and Hirlinger-Alexander, Jakob and Seibold, Matthias and Vollmer, Sergej and Sittig, Robert and Bauer, Stephanie and Braun, Fiona and Portalupi, Simone and Jetter, Michael and Michler, Peter}, doi = {10.1088/2633-4356/ad2522}, journal = {Materials for Quantum Technology}, month = {02}, title = {Growth of telecom C-band In(Ga)As quantum dots for silicon quantum photonics}, volume = 4, year = 2024 }
3. Strobel, T., Kazmaier, S., Bauer, T., Schäfer, M., Choudhary, A., Sharma, N. L., Joos, R., Nawrath, C., Weber, J. H., Nie, W., Bhayani, G., Wagner, L., Bisquerra, A., Geitz, M., Braun, R.-P., Hopfmann, C., Portalupi, S. L., Becher, C., & Michler, P. (2024). High-fidelity distribution of triggered polarization-entangled telecom photons via a 36 km intra-city fiber network. Optica Quantum, 2, Article 4. https://doi.org/10.1364/OPTICAQ.530838
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  @article{Strobel:24, abstract = {Fiber-based distribution of triggered, entangled, single-photon pairs is a key requirement for the future development of terrestrial quantum networks. In this context, semiconductor quantum dots (QDs) are promising candidates for deterministic sources of on-demand polarization-entangled photon pairs. So far, the best QD polarization-entangled-pair sources emit in the near-infrared wavelength regime, where the transmission distance in deployed fibers is limited. Here, to be compatible with existing fiber network infrastructures, bi-directional polarization-conserving quantum frequency conversion (QFC) is employed to convert the QD emission from 780 nm to telecom wavelengths. We show the preservation of polarization entanglement after QFC (fidelity to Bell state F $\varphi$ $+$,c o n v $=$0.972{\textpm}0.003) of the biexciton transition. As a step toward real-world applicability, high entanglement fidelities (F $\varphi$ $+$,l o o p $=$0.945{\textpm}0.005) after the propagation of one photon of the entangled pair along a 35.8 km field-installed standard single mode fiber link are reported. Furthermore, we successfully demonstrate a second polarization-conserving QFC step back to 780 nm preserving entanglement (F $\varphi$ $+$,b a c k $=$0.903{\textpm}0.005). This further prepares the way for interfacing quantum light to various quantum memories.}, author = {Strobel, Tim and Kazmaier, Stefan and Bauer, Tobias and Sch\"{a}fer, Marlon and Choudhary, Ankita and Sharma, Nand Lal and Joos, Raphael and Nawrath, Cornelius and Weber, Jonas H. and Nie, Weijie and Bhayani, Ghata and Wagner, Lukas and Bisquerra, Andr\'{e} and Geitz, Marc and Braun, Ralf-Peter and Hopfmann, Caspar and Portalupi, Simone L. and Becher, Christoph and Michler, Peter}, doi = {10.1364/OPTICAQ.530838}, journal = {Optica Quantum}, month = {08}, number = 4, pages = {274--281}, publisher = {Optica Publishing Group}, title = {High-fidelity distribution of triggered polarization-entangled telecom photons via a 36 km intra-city fiber network}, url = {https://opg.optica.org/opticaq/abstract.cfm?URI=opticaq-2-4-274}, volume = 2, year = 2024 }
  Link
  https://opg.optica.org/opticaq/abstract.cfm?URI=opticaq-2-4-274
4. Yang, J., Jiang, Z., Benthin, F., Hanel, J., Fandrich, T., Joos, R., Bauer, S., Kolatschek, S., Hreibi, A., Rugeramigabo, E. P., Jetter, M., Portalupi, S. L., Zopf, M., Michler, P., Kück, S., & Ding, F. (2024). High-rate intercity quantum key distribution with a semiconductor single-photon source. Light: Science & Applications, 13, Article 1. https://doi.org/10.1038/s41377-024-01488-0
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  @article{Yang2024, abstract = {Quantum key distribution (QKD) enables the transmission of information that is secure against general attacks by eavesdroppers. The use of on-demand quantum light sources in QKD protocols is expected to help improve security and maximum tolerable loss. Semiconductor quantum dots (QDs) are a promising building block for quantum communication applications because of the deterministic emission of single photons with high brightness and low multiphoton contribution. Here we report on the first intercity QKD experiment using a bright deterministic single photon source. A BB84 protocol based on polarisation encoding is realised using the high-rate single photons in the telecommunication C-band emitted from a semiconductor QD embedded in a circular Bragg grating structure. Utilising the 79{\thinspace}km long link with 25.49{\thinspace}dB loss (equivalent to 130{\thinspace}km for the direct-connected optical fibre) between the German cities of Hannover and Braunschweig, a record-high secret key bits per pulse of 4.8{\thinspace}{\texttimes}{\thinspace}10−5 with an average quantum bit error ratio of{\thinspace}{\textasciitilde}{\thinspace}0.65{\%} are demonstrated. An asymptotic maximum tolerable loss of 28.11{\thinspace}dB is found, corresponding to a length of 144{\thinspace}km of standard telecommunication fibre. Deterministic semiconductor sources therefore challenge state-of-the-art QKD protocols and have the potential to excel in measurement device independent protocols and quantum repeater applications.}, author = {Yang, Jingzhong and Jiang, Zenghui and Benthin, Frederik and Hanel, Joscha and Fandrich, Tom and Joos, Raphael and Bauer, Stephanie and Kolatschek, Sascha and Hreibi, Ali and Rugeramigabo, Eddy Patrick and Jetter, Michael and Portalupi, Simone Luca and Zopf, Michael and Michler, Peter and K{\"u}ck, Stefan and Ding, Fei}, day = 02, doi = {10.1038/s41377-024-01488-0}, issn = {2047-7538}, journal = {Light: Science {\&} Applications}, month = {07}, number = 1, pages = 150, title = {High-rate intercity quantum key distribution with a semiconductor single-photon source}, url = {https://doi.org/10.1038/s41377-024-01488-0}, volume = 13, year = 2024 }
  Link
  https://doi.org/10.1038/s41377-024-01488-0
5. Thomas, S. E., Wagner, L., Joos, R., Sittig, R., Nawrath, C., Burdekin, P., de Buy Wenniger, I. M., Rasiah, M. J., Huber-Loyola, T., Sagona-Stophel, S., Höfling, S., Jetter, M., Michler, P., Walmsley, I. A., Portalupi, S. L., & Ledingham, P. M. (2024). Deterministic storage and retrieval of telecom light from a quantum dot single-photon source interfaced with an atomic quantum memory. Science Advances, 10, Article 15. https://doi.org/10.1126/sciadv.adi7346
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  @article{doi:10.1126/sciadv.adi7346, abstract = {A hybrid interface of solid-state single-photon sources and atomic quantum memories is a long sought-after goal in photonic quantum technologies. Here, we demonstrate deterministic storage and retrieval of light from a semiconductor quantum dot in an atomic ensemble quantum memory at telecommunications wavelengths. We store single photons from an indium arsenide quantum dot in a high-bandwidth rubidium vapor–based quantum memory, with a total internal memory efficiency of (12.9 ± 0.4)\%. The signal-to-noise ratio of the retrieved light field is 18.2 ± 0.6, limited only by detector dark counts. A quantum dot single-photon source and an atomic quantum memory are key interface components for future quantum networks.}, author = {Thomas, Sarah E. and Wagner, Lukas and Joos, Raphael and Sittig, Robert and Nawrath, Cornelius and Burdekin, Paul and de Buy Wenniger, Ilse Maillette and Rasiah, Mikhael J. and Huber-Loyola, Tobias and Sagona-Stophel, Steven and Höfling, Sven and Jetter, Michael and Michler, Peter and Walmsley, Ian A. and Portalupi, Simone L. and Ledingham, Patrick M.}, doi = {10.1126/sciadv.adi7346}, eprint = {https://www.science.org/doi/pdf/10.1126/sciadv.adi7346}, journal = {Science Advances}, number = 15, pages = {eadi7346}, title = {Deterministic storage and retrieval of telecom light from a quantum dot single-photon source interfaced with an atomic quantum memory}, url = {https://www.science.org/doi/abs/10.1126/sciadv.adi7346}, volume = 10, year = 2024 }
  Link
  https://www.science.org/doi/abs/10.1126/sciadv.adi7346
6. Joos, R., Bauer, S., Rupp, C., Kolatschek, S., Fischer, W., Nawrath, C., Vijayan, P., Sittig, R., Jetter, M., Portalupi, S. L., & Michler, P. (2024). Coherently and Incoherently Pumped Telecom C-Band Single-Photon Source with High Brightness and Indistinguishability. Nano Letters, 24, 28. https://pubs.acs.org/doi/full/10.1021/acs.nanolett.4c01813
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  @article{joos2024coherently, author = {Joos, Raphael and Bauer, Stephanie and Rupp, Christian and Kolatschek, Sascha and Fischer, Wolfgang and Nawrath, Cornelius and Vijayan, Ponraj and Sittig, Robert and Jetter, Michael and Portalupi, Simone L. and Michler, Peter}, journal = {Nano Letters}, month = {07}, pages = 28, title = {Coherently and Incoherently Pumped Telecom C-Band Single-Photon Source with High Brightness and Indistinguishability}, url = {https://pubs.acs.org/doi/full/10.1021/acs.nanolett.4c01813}, volume = 24, year = 2024 }
  Link
  https://pubs.acs.org/doi/full/10.1021/acs.nanolett.4c01813
2023
1. Nawrath, C., Joos, R., Kolatschek, S., Bauer, S., Pruy, P., Hornung, F., Fischer, J., Huang, J., Vijayan, P., Sittig, R., Jetter, M., Portalupi, S. L., & Michler, P. (2023). Bright Source of Purcell-Enhanced, Triggered, Single Photons in the Telecom C-Band. Advanced Quantum Technologies. https://doi.org/10.1002/qute.202300111
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  @article{nawrath2023bright, abstract = {Several emission features mark semiconductor quantum dots as promisingnon-classical light sources for prospective quantum implementations. Forlong-distance transmission and Si-based on-chip processing, the possibility tomatch the telecom C-band is decisive, while source brightness and highsingle-photon purity are key features in virtually any quantumimplementation. An InAs/InGaAs/GaAs quantum dot emitting in the telecomC-band coupled to a circular Bragg grating is presented here. This cavitystructure stands out due to its high broadband collection efficiency and highattainable Purcell factors. Here, simultaneously high brightness with afiber-coupled single-photon count rate of 13.9 MHz for an excitationrepetition rate of 228 MHz (first-lens single-photon collection efficiency≈17%for NA=0.6), while maintaining a low multi-photon contribution ofg(2)(0)=0.0052 is demonstrated. Moreover, the compatibility withtemperatures of up to 40 K attainable with compact cryo coolers, furtherunderlines the suitability for out-of-the-lab implementations}, author = {Nawrath, Cornelius and Joos, Raphael and Kolatschek, Sascha and Bauer, Stephanie and Pruy, Pascal and Hornung, Florian and Fischer, Julius and Huang, Jiasheng and Vijayan, Ponraj and Sittig, Robert and Jetter, Michael and Portalupi, Simone Luca and Michler, Peter}, issn = {2511-9044}, journal = {Advanced Quantum Technologies}, month = {08}, title = {Bright Source of Purcell-Enhanced, Triggered, Single Photons in the Telecom C-Band}, url = {https://doi.org/10.1002/qute.202300111}, year = 2023 }
  Link
  https://doi.org/10.1002/qute.202300111
2021
1. Wang, Q., Maisch, J., Tang, F., Zhao, D., Yang, S., Joos, R., Portalupi, S. L., Michler, P., & Smet, J. H. (2021). Highly Polarized Single Photons from Strain-Induced Quasi-1D Localized Excitons in WSe2. Nano Letters, 21, Article 17. https://doi.org/10.1021/acs.nanolett.1c01927
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  @article{doi:10.1021/acs.nanolett.1c01927, abstract = { Single photon emission from localized excitons in two-dimensional (2D) materials has been extensively investigated because of its relevance for quantum information applications. Prerequisites are the availability of photons with high purity polarization and controllable polarization orientation that can be integrated with optical cavities. Here, deformation strain along edges of prepatterned square-shaped substrate protrusions is exploited to induce quasi-one-dimensional (1D) localized excitons in WSe2 monolayers as an elegant way to get photons that fulfill these requirements. At zero magnetic field, the emission is linearly polarized with 95\% purity because exciton states are valley hybridized with equal shares of both valleys and predominant emission from excitons with a dipole moment along the elongated direction. In a strong field, one valley is favored and the linear polarization is converted to high-purity circular polarization. This deterministic control over polarization purity and orientation is a valuable asset in the context of integrated quantum photonics. }, author = {Wang, Qixing and Maisch, Julian and Tang, Fangdong and Zhao, Dong and Yang, Sheng and Joos, Raphael and Portalupi, Simone Luca and Michler, Peter and Smet, Jurgen H.}, doi = {10.1021/acs.nanolett.1c01927}, eprint = {https://doi.org/10.1021/acs.nanolett.1c01927}, journal = {Nano Letters}, note = {PMID: 34424710}, number = 17, pages = {7175-7182}, title = {Highly Polarized Single Photons from Strain-Induced Quasi-1D Localized Excitons in WSe2}, url = {/brokenurl# https://doi.org/10.1021/acs.nanolett.1c01927 }, volume = 21, year = 2021 }
  Link
  /brokenurl# https://doi.org/10.1021/acs.nanolett.1c01927
2020
1. Yang, J., Nawrath, C., Keil, R., Joos, R., Zhang, X., Höfer, B., Chen, Y., Zopf, M., Jetter, M., Portalupi, S. L., Ding, F., Michler, P., & Schmidt, O. G. (2020). Quantum dot-based broadband optical antenna for efficient extraction of single photons in the telecom O-band. Opt. Express, 28, Article 13. https://doi.org/10.1364/OE.395367
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  @article{Yang:20, abstract = {Long-distance fiber-based quantum communication relies on efficient non-classical light sources operating at telecommunication wavelengths. Semiconductor quantum dots are promising candidates for on-demand generation of single photons and entangled photon pairs for such applications. However, their brightness is strongly limited due to total internal reflection at the semiconductor/vacuum interface. Here we overcome this limitation using a dielectric antenna structure. The non-classical light source consists of a gallium phosphide solid immersion lens in combination with a quantum dot nanomembrane emitting single photons in the telecom O-band. With this device, the photon extraction is strongly increased in a broad spectral range. A brightness of 17\% (numerical aperture of 0.6) is obtained experimentally, with a single photon purity of g(2)(0)$=$0.049{\textpm}0.02 at saturation power. This brings the practical implementation of quantum communication networks one step closer.}, author = {Yang, Jingzhong and Nawrath, Cornelius and Keil, Robert and Joos, Raphael and Zhang, Xi and H\"{o}fer, Bianca and Chen, Yan and Zopf, Michael and Jetter, Michael and Portalupi, Simone Luca and Ding, Fei and Michler, Peter and Schmidt, Oliver G.}, doi = {10.1364/OE.395367}, journal = {Opt. Express}, month = {06}, number = 13, pages = {19457--19468}, publisher = {OSA}, title = {Quantum dot-based broadband optical antenna for efficient extraction of single photons in the telecom O-band}, url = {http://www.opticsexpress.org/abstract.cfm?URI=oe-28-13-19457}, volume = 28, year = 2020 }
  Link
  http://www.opticsexpress.org/abstract.cfm?URI=oe-28-13-19457

Raphael Joos

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Raphael Joos

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