Title of seminar: Quantum interferometric metrology with entangled photons

Abstract:

Quantum metrology exploits uniquely quantum properties such as entanglement and quantum interference to improve the precision of measurements beyond what is achievable with classical resources. While quantum-enhanced sensing has demonstrated remarkable performances in laboratory environments, transferring these advantages to practical fiber-based platforms remains a significant challenge due to optical losses and experimental imperfections.

In this seminar, I will present our recent work on quantum interferometric metrology using entangled photons in telecom optical fibers. After introducing the concepts of quantum advantage and a Fisher information framework for realistic quantum sensing, I will present the experimental demonstration of quantum-enhanced phase sensing in an all-fiber Mach–Zehnder interferometer. These results illustrate the potential of fiber-integrated quantum photonics for practical quantum sensing. Then, I will introduce our recent work on quantum-enhanced phase tracking through spectral noise reduction and finally discuss how quantum communication techniques, including QKD-based synchronization, can be leveraged to enable long-distance quantum sensor networks.

The seminar will illustrate how quantum photonic technologies are progressively moving from proof-of-principle demonstrations toward practical quantum sensing systems compatible with existing telecommunication infrastructures.

Title of seminar: Quantum logic control of molecular and transition-metal ions

Abstract:

Extending quantum control to increasingly complex systems is essential for advancing quantum technologies and probing fundamental physics. Molecules, in particular, serve as highly sensitive systems for detecting symmetry violations that may reveal physics beyond the Standard Model. However, their complex level structure makes quantum-state control challenging.

Quantum logic spectroscopy offers a promising path forward for molecular ions: a well-controlled atomic ion is co-trapped with a molecular ion and enables manipulation and readout of its quantum state via shared motional modes. I will present an overview of our latest results and concepts in quantum logic control of molecular ions. As we progress toward quantum logic spectroscopy of single molecular MgH⁺ ions, we are also assessing the broader applicability of these techniques to other ionic species. Recently, we demonstrated quantum logic control of a single titanium ion [1,2], showing that these methods can be extended to previously inaccessible atomic systems.

By enhancing control over new classes of ions, our work opens the door to novel applications in quantum technology and fundamental physics, making an extended range of species available for precision spectroscopy.

References:

[1] Rehmert et al. Quantum Logic Control of a Transition Metal Ion, Physical Review Letters 134, 113201 (2025)

[2] Rehmert et al. Landé g Factor Measurement of ⁴⁸Ti⁺ Using Simultaneous Comagnetometry and Quantum Logic Spectroscopy, Physical Review Letters 136, 083203 (2026)

Title of seminar: UV-Dual Comb Spectroscopy using a bidirectional mode-locked femtosecond Ti:Sapphire ring laser

Abstract :

The development of broadband, precise, and rapid molecular spectroscopy addresses current challenges in gas detection within dynamic and complex environments. I will present dual-comb spectroscopy, a technique that is particularly well suited to meeting these challenges. At the Institute of Light and Matter (Lyon), we are developing dual-comb spectroscopy in the UV spectral range to probe highly reactive species such as radicals. I will introduce the experimental dual-comb source we have developed, based on a mode-locked femtosecond Ti ring laser, discuss its unique characteristics and present spectroscopic results obtained in both the IR and UV spectral regions.

Title of seminar: Tests of fundamental physics using ytterbium ions

Abstract :

I will present the first results from my postdoc at PTB in Braunschweig, Germany. Trapped ions are widely used in optical clocks and fundamental physics. Among them, the forbidden electric octupole (E3) transition in 173Yb⁺ offers key advantages, including an extremely narrow natural linewidth and high sensitivity to physics beyond the Standard Model. The large electric quadrupole moment of its deformed nucleus is predicted to enhance this forbidden transition. I will show how we confirmed this effect and observed hyperfine-state-dependent quenching, paving the way toward multi-ion clocks using 173Yb⁺. I will further show how the rich hyperfine structure can be used to probe the nuclear properties of 173Yb⁺, making it a particularly promising candidate for searches of a fifth force using isotope shifts measurements and King plot analysis.