Light Sources for Quantum Communication in the 1300 nm Spectral Range
Final Report Abstract
The second quantum revolution has underscored the critical role of quantum-light sources in advancing quantum nanophotonics. Single photons and entangled photon pairs are essential for quantum circuits and long-distance quantum communication, serving as photonic qubits for secure information transfer. Unlike non-deterministic sources such as attenuated lasers or parametric down-conversion, semiconductor quantum dots (QDs) provide an ideal platform for triggered quantum-light generation. To meet the stringent requirements for quantum applications — such as high photon extraction efficiency, indistinguishability, and entanglement — QD-based sources must be fabricated using deterministic fabrication technologies. While InGaAs QDs emitting in the 900-960 nm range have shown near-ideal performance, these wavelengths are unsuitable for fiber-optic communication due to high transmission losses. This limitation has shifted focus of QD development to telecom wavelengths (1.3 µm in the O-band and 1.55 µm in the C-band), which are better suited for long-distance quantum networks and repeater protocols. Advances in epitaxial growth and single-photon detectors have enabled telecom-wavelength QD sources, but challenges such as low photon-extraction efficiency and indistinguishability persist. This project aimed to address these challenges by developing cavity-enhanced QD-based single-photon sources (SPSs) emitting at telecom wavelengths. Numerical optimization of microcavity designs, such as hybrid distributed Bragg reflectors, demonstrated significant improvements in photon extraction efficiency (PEE), reaching 83% with broadband enhancement. Advanced designs incorporating oxide apertures achieved high light-matter coupling and lateral confinement, with calculated PEE values up to 67%. Epitaxial growth efforts focused on lowdensity O-band QDs with high quantum efficiency of (85±10)%. A breakthrough in fabrication techniques was achieved with machine learning (ML)-enhanced in situ electron beam lithography (iEBL), which improved QD alignment accuracy significantly. Compared to conventional iEBL, ML-enhanced iEBL reduced deviations to less than 100 nm, enabling precise deterministic fabrication of QD devices such as circular Bragg grating (CBG) resonators. Optical studies validated these advancements, with time-resolved photoluminescence measurements confirming the high optical quality of the QDs. Despite organizational challenges, such as the termination of a key collaboration, the project delivered significant progress in quantum-light source development. Results included optimized device designs, high-precision fabrication techniques, and fundamental insights into QD properties. These outcomes pave the way for high-performance quantum-light sources, essential for future quantum communication and networking technologies, including scalable twosource quantum interference and device-independent quantum key distribution.
Publications
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Design of electrically driven single-photon source based on intra-cavity contacted microcavity with oxide-confined optical apertures emitting at 1.3 μm. Journal of Physics: Conference Series, 2103(1), 012181.
Blokhin, S. A.; Bobrov, M. A.; Maleev, N. A.; Blokhin, A. A.; Vasyl’ev, A. P.; Kuzmenkov, A. G.; Shchukin, V. A.; Ledentsov, N. N.; Reitzenstein, S. & Ustinov, V. M.
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Design optimization for bright electrically-driven quantum dot single-photon sources emitting in telecom O-band. Optics Express, 29(5), 6582.
Blokhin, S. A.; Bobrov, M. A.; Maleev, N. A.; Donges, J. N.; Bremer, L.; Blokhin, A. A.; Vasil’ev, A. P.; Kuzmenkov, A. G.; Kolodeznyi, E. S.; Shchukin, V. A.; Ledentsov, N. N.; Reitzenstein, S. & Ustinov, V. M.
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Quantum efficiency and oscillator strength of InGaAs quantum dots for single-photon sources emitting in the telecommunication O-band. Applied Physics Letters, 119(6).
Große, Jan; Mrowiński, Paweł; Srocka, Nicole & Reitzenstein, Stephan
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The Design of an Electrically-Driven Single Photon Source of the 1.3-μm Spectral Range Based on a Vertical Microcavity with Intracavity Contacts. Technical Physics Letters, 47(3), 222-226.
Blokhin, S. A.; Bobrov, M. A.; Maleev, N. A.; Blokhin, A. A.; Vasil’ev, A. P.; Kuz’menkov, A. G.; Kolodeznyi, E. S.; Shchukin, V. A.; Ledentsov, N. N.; Reitzenstein, S. & Ustinov, V. M.
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Fiber-coupled quantum light sources based on solid-state quantum emitters. Materials for Quantum Technology, 2(4), 042002.
Bremer, Lucas; Rodt, Sven & Reitzenstein, Stephan
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High efficiency electrically–driven single photon sources: advanced design concepts. Quantum Sensing and Nano Electronics and Photonics XVIII, 35. SPIE.
Ledentsov, Nikolay; Blokhin, Sergey A.; Bobrov, Mikhail A.; Maleev, Nikolay A.; Blokhin, Alexey A.; Shchukin, Vitaly A.; Ledentsov, Nikolay N.; Reitzenstein, Stephan & Ustinov, Viktor M.
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Machine learning enhanced in situ electron beam lithography of photonic nanostructures. Nanoscale, 14(39), 14529-14536.
Donges, Jan; Schlischka, Marvin; Shih, Ching-Wen; Pengerla, Monica; Limame, Imad; Schall, Johannes; Bremer, Lucas; Rodt, Sven & Reitzenstein, Stephan
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Quantum dots for photonic quantum information technology. Advances in Optics and Photonics, 15(3), 613.
Heindel, Tobias; Kim, Je-Hyung; Gregersen, Niels; Rastelli, Armando & Reitzenstein, Stephan
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Telecom-band quantum dot technologies for long-distance quantum networks. Nature Nanotechnology, 18(12), 1389-1400.
Yu, Ying; Liu, Shunfa; Lee, Chang-Min; Michler, Peter; Reitzenstein, Stephan; Srinivasan, Kartik; Waks, Edo & Liu, Jin
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Assessing the Alignment Accuracy of State-of-the-Art Deterministic Fabrication Methods for Single Quantum Dot Devices. ACS Photonics, 11(3), 1012-1023.
Madigawa, Abdulmalik A.; Donges, Jan N.; Gaál, Benedek; Li, Shulun; Jacobsen, Martin Arentoft; Liu, Hanqing; Dai, Deyan; Su, Xiangbin; Shang, Xiangjun; Ni, Haiqiao; Schall, Johannes; Rodt, Sven; Niu, Zhichuan; Gregersen, Niels; Reitzenstein, Stephan & Munkhbat, Battulga
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Roadmap on specialty optical fibers. Journal of Physics: Photonics, 7(1), 012501.
Ferreira, Mário F. S.; Rehan, Mohd; Mishra, Vishwatosh; Varshney, Shailendra Kumar; Poletti, Francesco; Phuoc, Trung Hoa Nguyen; Wang, Weichao; Zhang, Qinyuan; Du, Wenyu; Yu, Benli; Hu, Zhijia; Feng, Xian; Shi, Jindan; Anjali, N.A.; Kumar, Sunil; Kamrádek, Michal; Paul, Mukul Chandra; Abedin, Kazi; Kibler, Bertrand ... & Reitzenstein, Stephan
