VTT’s Post

🕰️ Austria installs a state-of-the-art Optical clock Since the end of September, the Austrian Federal Office of Metrology and Surveying (BEV) has been operating one of the world’s first commercially available optical clocks – the TOPTICLOCK. This new ytterbium⁺ ion clock marks a major leap in timing precision and strengthens Austria’s role within the international timekeeping community. Installed in Vienna on September 29, the high-precision Yb⁺ ion clock enhances Austria’s contribution to the global time network. The system was procured as part of the FFG-funded AQUclock project in collaboration with Vienna University of Technology and delivered by TOPTICA Photonics. At BEV, the Yb⁺ clock will play a key role in the realization and monitoring of UTC (Coordinated Universal Time). By continuously providing ultra-precise timing data, Austria underscores its commitment to technological excellence and solidifies its position in the world’s most accurate timekeeping infrastructure. ➡️ Full story (in German): https://lnkd.in/gDuZiwUB Photo: © BEV / Bernhard Rotter

We are excited to announce the publication of our latest work in Optica Quantum, where we explore novel methods for creating frequency-entangled photon pairs using quantum dots (QDs) embedded to a waveguide. 
In our theoretical investigation, we present a shaping frequency entangling gate (FrEnGATE) for single photons. This approach leverages the atomic-like properties of a quantum dot to achieve frequency-dependent two-photon transitions at telecom wavelengths. It is achieved by employing an adiabatic elimination technique resulting in efficient frequency entanglement generation without the need for post-selection or auxiliary photons. Our findings offer measurement-free approach to generate time-frequency cluster states which pave the way for new quantum sensing (time and frequency shift estimation) and quantum communications. https://lnkd.in/e6_3BZuB #TelecomParis #IMT #IPP #QSNP #HorizonEurope #CNRS #CNR #SapienzaUniversity #OpticaQuantum

100um Fiber Collimator: Why is 1550nm the Most Commonly Used Wavelength? In fiber optic communication, sensing, and precision optical systems, fiber collimators are crucial bridges connecting optical fibers to free-space optical paths. When you see a fiber collimator specified as “100μm,” it is almost always designed and optimized for the 1550nm wavelength. This is not a coincidence, but a necessary choice determined by fiber characteristics, physical laws, and industry demands. Read more https://lnkd.in/ggmA9yfa #xhphotoelectric #opticalswitch #NetworkSwitch #communication #coupler #Collimator #Data #fiber #optics #photonics #FiberOpticCirculator #VOA

This paper proposes a resource-efficient array #undersampling structure which is distinctive in that each array element only connects to one branch of the #Modulated #Wideband #Converter (#MWC), and the modulated signals in different branches have identical periods but different waveforms. The proposed structure integrates spatial sampling by array elements and temporal undersampling by the MWC. A signal model is developed for the proposed sampling structure, which can deal with more general scenarios, involving #multiple #subband #signals, and #cross-#band #signals. Joint #spectrum #sensing algorithms are proposed based on compressed sensing and subspace decomposition. Additionally, multi-resolution grid optimization strategy is designed to eliminate grid effect with low computational complexity. They also analyze the impact of structural parameters on algorithm performance, which reveals that the number of array elements determines the maximum number of signals that can be estimated within a subband, while the equivalent total number of channels of the reception system determines the maximum number of signals that the system can estimate. ---- Liang Liu, Zhan Zhang, Xinyun Zhang, Ping Wei, Jiancheng An, Hongbin Li More details can be found at this link: https://lnkd.in/eEAWiBh5

This paper proposes a resource-efficient array #undersampling structure which is distinctive in that each array element only connects to one branch of the #Modulated #Wideband #Converter (#MWC), and the modulated signals in different branches have identical periods but different waveforms. The proposed structure integrates spatial sampling by array elements and temporal undersampling by the MWC. A signal model is developed for the proposed sampling structure, which can deal with more general scenarios, involving #multiple #subband #signals, and #cross-#band #signals. Joint #spectrum #sensing algorithms are proposed based on compressed sensing and subspace decomposition. Additionally, multi-resolution grid optimization strategy is designed to eliminate grid effect with low computational complexity. They also analyze the impact of structural parameters on algorithm performance, which reveals that the number of array elements determines the maximum number of signals that can be estimated within a subband, while the equivalent total number of channels of the reception system determines the maximum number of signals that the system can estimate. ---- Liang Liu, Zhan Zhang, Xinyun Zhang, Ping Wei, Jiancheng An, Hongbin Li More details can be found at this link: https://lnkd.in/eEAWiBh5

📣 Celebrating Impactful Research in Antenna Array Beamsteering! 🚀 🧠 Uniform Linear #Antenna Array Beamsteering Based on #Phase-Locked Loops Authors: Anil Chepala, Vincent Fusco, Umair Naeem and Adrian McKernan This work presents a comprehensive tutorial-style exploration of uniform linear antenna arrays (ULAs) and electronic beamsteering using phase-locked loops (PLLs) — bridging theory, practical implementation, and experimental verification. Read the full open access article here: https://lnkd.in/dGzdsvKq #ResearchImpact #PhasedArrays #Beamsteering #WirelessCommunication #ElectronicsJournal

🚀 New preprint out! I’m happy to share our latest work, “Tailored Error Mitigation for Single-Qubit Magnetometry”, recently uploaded as a preprint together with my colleagues Miriam Resch, Dennis Herb, Joachim Ankerhold and Dominik Maile. 🔍 What’s it about? Quantum sensors promise unprecedented sensitivity and spatial resolution, but their performance is often limited by complex, device-specific noise. In this work, we introduce a tailored quantum error mitigation strategy for single-qubit sensing that: • optimally leverages prior noise characterization via channel tomography, • efficiently mitigates general (including non-Markovian) noise processes, and • identifies optimal sensing times to achieve the best possible sensitivity. 🧲 Why it matters Using single NV-center magnetometry as a benchmark, we show that our approach can recover the best achievable sensitivity even in the presence of realistic, complex environments (spin baths and phonons). Importantly, the protocol is experimentally feasible and adaptable, requiring only a small number of tailored circuits. 📄 The preprint is available here: 👉 https://lnkd.in/gmBpYznN Many thanks again to the people I worked with, who made this possible! #QuantumSensing #QuantumErrorMitigation #NVcenter #Preprint #QuantumTechnology #Magnetometry

Eugenio Maggiolini (Johannes Kepler University Linz, Austria) delivered an insightful talk on "Quantum nonlinear optics in exciton-polariton circuits." A deep dive into how hybrid light-matter quasi-particles (exciton-polaritons) are being harnessed for next-generation quantum circuits. 💡🔬

Quantum key distribution over fiber networks faces a persistent challenge: balancing detector efficiency at one end with low transmission loss at the other. Our team from Quantum Optics Jena GmbH together with Friedrich-Schiller-Universität Jena has developed an entangled photon source that addresses both simultaneously. Using type-0 SPDC in a crossed-crystal configuration, we generate photon pairs at 680 nm and 1550 nm – a wavelength combination not previously reported. This pairing leverages peak Si-SPAD detection efficiency in the visible range while exploiting minimal fiber loss in the telecom C-band. The source delivers 300 GHz spectral bandwidth with brightness up to 1.9 × 10³ pairs s⁻¹ mW⁻¹ GHz⁻¹, and heralding efficiencies of 18% (signal) and 34% (idler). Preprint now available on arXiv: https://lnkd.in/d7RacXJV Authors: Laurentiu Dosan, Alek Lagarrigue, Alessandro Zannotti, Tushar Parab, Yannick Folwill, Fabian Steinlechner, Oliver de Vries #QuantumCommunication #EntangledPhotonSource #QuantumOpticsJena Thanks for supporting this work within the SQuIRRL project (https://lnkd.in/dPW-P2r5) to Bundesministerium für Forschung, Technologie und Raumfahrt.

✨Editor's Choice Article✨  Zhu, M.; Gao, P.; Cai, S.; Zhang, N.; Wu, B.; Liu, Y.; Yin, B.; Wang, M. High-Sensitivity Magnetic Field Sensor Based on an Optoelectronic Oscillator with a Mach–Zehnder Interferometer. Sensors 2025, 25, 1621. 🏫Beijing Jiaotong University, China United Network Communications Group Corporation Limited, Beijing University of Posts and Telecommunications, Ocean University of China ✨A high-sensitivity magnetic field sensor based on an optoelectronic oscillator (OEO) with a Mach–Zehnder interferometer (MZI) is proposed and experimentally demonstrated. The magnetic field sensor consists of a fiber Mach–Zehnder interferometer, with the lower arm of the interferometer wound around a magnetostrictive transducer. Due to the magnetostrictive effect, an optical phase shift induced by magnetic field variation is generated between two orthogonal light waves transmitted in the upper and lower arms of the MZI. The polarization-dependent property of a Mach–Zehnder modulator (MZM) is utilized to transform the magnetostrictive phase shift into the phase difference between the sidebands and optical carrier, which is mapped to the oscillating frequency upon the completion of an OEO loop. High-sensitivity magnetic field sensing is achieved by observing the frequency shift of the radio frequency (RF) signal. Temperature-induced cross-sensitivity is mitigated through precise length matching of the MZI arms. In the experiment, the high magnetic field sensitivity of 6.824 MHz/mT with a range of 25 mT to 25.3 mT is achieved and the sensing accuracy measured by an electrical spectrum analyzer (ESA) at “maxhold” mode is 0.002 mT. The proposed sensing structure has excellent magnetic field detection performance and provides a solution for temperature-insensitive magnetic field detection, which would have broad application prospects. https://lnkd.in/efupVRAi