Status & Perspectives in Science & Education

153 152 Principal Scientist Profiles Fabian Steinlechner Fabian Steinlechner Principal Scientist Profiles PROFESSOR FOR EXPERIMENTAL QUANTUM INFORMATION AT THE INSTITUTE OF APPLIED PHYSICS Dr. Fabian Steinlechner received his PhD in 2015 from ICFO (Barcelona, Spain) where his doctoral research focused on the development of quantum light sources for applications in Space. As a postdoctoral fellow at the Institute for Quantum Optics and Quantum Information in Vienna, he contributed to the application of entangled photons in loophole-free tests of non-locality, quantum sensing, high-dimensional quantum information processing, and long-distance quantum communication in free-space and fiber links. In 2018, he established the “Quantum Communication Technologies” and “Photonic Quantum Information” groups at Fraunhofer IOF Jena. In 2023, Fabian Steinlechner was appointed as a full professor for Experimental Quantum Information at the Institute of Applied Physics at the University of Jena. FABIAN STEINLECHNER RESEARCH AREAS Entangled photons are a key resource in quantum technology. They act as low-noise probes in imaging and sensing, as versatile information carriers in information processing and communication networks or as tamper-proof padlocks for cryptography. Dr. Steinlechner‘s research focuses on photonic technologies for generating and manipulating complex quantum states of light for applications in remote sensing, long-range quantum communication, quantum information processing and distributed quantum networks. Research topics include: • Tailoring the spatial- and spectral structure of biphotons generated via downconversion • High-dimensional quantum information processing in the spatial and temporal domain • Generating non-classical states of light for applications in ranging and remote sensing • Quantum hardware and adaptive optics for satellitebased quantum communication • Distributed quantum information processing enabled by high-dimensional photonic entanglement and hyperentanglement TEACHING FIELDS • Quantum communication RESEARCH METHODS The group utilizes modern experimental equipment including: • Ultra-bright entangled photon sources • Pulsed and cw-lasers at different wavelengths • Wavelength-division multiplexing technology • Single photon detectors and time-tagging electronics • Ultra-fast electro-optic modulators and pulse shapers • Spatial light modulators and adaptive optics [1] Brambila et al., Opt. Express 31, 16107 (2023). [2] Baghdasaryan et al., Phys. Rev. A 101, 043844 (2020). [3] Sephton et al., Optics Letters 44 (2019). [3] Baghdasaryan et al., Phys. Rev. A 101, 043844 (2020). [4] Chen et al., Phys. Rev. A 21 (2020). [5] Chen et al., Npj Quantum Information 5 (2019). [6] Ecker et al., Physical Review X, 9 (2019). [7] Beckert et al., Free-Space Laser Communications XXXI, 10910 (2019). [8] Bmbf, Qunet-Alpha, www.forschung-it-sicherheit-kommunikationssysteme. de/projekte/qunet-alpha [9] Wengerowsky et al., npj Quantum Information 6, 1 (2020). RECENT RESEARCH RESULTS Recent research results include the demonstration of polarization-entangled photon sources with world record pair generation rates [1], the manipulation and detection of spatially-encoded [2-3] and frequency-encoded quantum states [4] for high-dimensional quantum information processing, novel approaches in quantum-enhanced sensing [5], as well as the exploitation of high-dimensional entanglement in noise-resilient quantum communication [6]. The group is also involved in collaborative efforts aimed at advancing quantum technology from laboratory to commercial application, in particular the design of quantum payloads for satellite deployment [7] and quantum communication systems for metropolitan free-space [8] and fiber networks [9]. ENTANGLEMENT-BASED QUANTUM KEY DISTRIBUTION The group recently established a quantum-secure communication testbed, thereby showcasing local competences along the entire quantum photonics process chain: Figure a) Polarization-entangled photons (photon A and photon B) are generated in a spontaneous parametric down conversion process (SPDC). Photon A is sent to Alice via an optical single-mode fiber, and Photon B is guided to a large-aperture folded mirror telescope and transmitted to Bob via an optical free-space link. The link transmission is continuously monitored and optimized using fast beam steering mirrors. The polarization of individual photons is analyzed continuously and detection events are timestamped with respect to a local Rubidium clock. Residual clock drift is compensated for by continuously tracking the two-photon correlation peak. Figure b) Starting the measurements around midnight, the quantum bit error rate (QBER) slowly increases due to polarization misalignment and abruptly peaks at sunrise due to increased background counts. Ongoing R&D addresses autonomous long-term polarization tracking, optimized spatial filtering for daylight operation, as well as adaptive optics wave front correction for efficient coupling of photons into optical fiber networks. (left) Schematic representation of multi-plane light conversion for efficient manipulation and analysis of high-dimensional quantum states. (right) Spatial correlations of entangled photon pairs generated via parametric down conversion in a LaguerreGauss detection basis. Contact: Phone: + 49 3641 807 733 Email: fabian.steinlechner@uni-jena.de fabian.steinlechner@iof.fraunhofer.de

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