Johanna did her bachelor thesis with us, working on the characterization of an atomic beam. Now that the thesis is submitted and defended, she'll return to the lecture hall for her master studies: good luck! 

Welcome Felix, who re-joins our group for his PhD thesis. Felix studied in Heidelberg and already did an external master thesis with us, setting up the xenon two-photon spectroscopy experiment. After a short break, he now continues as a PhD student on the zinc experiment. Good luck with your work! 

Georg Enzian joins the group as permanent staff! Georg has studied here in Bonn before starting a PhD in Oxford on cavity optomechanics. He then moved on to Copenhagen and further on to a quantum computing company. Georg brings in a wealth of experience, and we are very glad to have him: welcome to the team! 

In the vicinity of Munich, LMU operates a unique observatory: an underground array of four ring lasers, arranged to the shape of a tetrahedron with a side length of 12 meters. The project is calles ROMY, which stands for ROtational Motions in seismologY. We are proud to contribute measurement technology and expertise to ROMY, and a careful characterization of the device has just been published with Review of Scientific Instruments (link: https://doi.org/10.1063/5.0242127⁷). 

Work around the extended Pentecost weekend has been quite successful: Anica's most recent paper on basic properties of frequency conversion in dense gases has been accepted by Optics Letters (DOI: 10.1364/OL.553732). We also have two new manuscripts on the arXiv: One is on our endeavour to generate 100+ mW of light at 213 nm (https://arxiv.org/abs/2506.08709⁸), the other one on the latest improvements in our frequency conversion business (https://arxiv.org/abs/2506.05989⁹). Enjoy reading them!

A dream comes true: all three Cluster applications of the physics department were successful and will now be funded for at least seven years. Apart from ML4Q, this includes the Color meets Flavor (CmF) initiative of our colleagues from high energy physics, as well as the Dynaverse initiative from our astronomy fellows. Coming back to quantum physics, also all existing Clusters of the Quantum Alliance were continued: a great success of both our department and our field of research. Congratulations to all winners, we are looking forward to another 7 years of intense work.

Two member of the Quantum Metrology team finished their theses: Tessa learned how to operate an active ring laser in a passive fashion: still some instabilities, but it's the first hybrid ring laser, world-wide: congratulations! Felix joined us from Heidelberg and worked on two-photon spectroscopy of a deep-UV transition in Xenon: now he can call himself a master of science! 

It's the end of the winter break and the beginning of the summer term, and there has been some shuffling within the team. Katrin and Priyanka finish their master theses: Katrin worked in the frequency conversion, while Priyanka had worked with us previously and now did a master thesis with our beloved friend Tommaso Calarco in Jülich. Benny joined us from Heidelberg for part of his master thesis on xenon spectroscopy, and Johanna will join us for her bachelor thesis on the Sr MOT experiment. And we welcome back Sascha, who officially begins his PhD thesis on the mercury experiment. All the best to all of you! 

Time passes quickly: we are celebrating already the 7th birthday of our research group. What started in April 2018 with no labs and no offices has grown into a vibrant team of nearly 20 people operating eight full-fledged optics labs. Sadly, it's also the end of the quMercury ERC project, which went through two extensions and shaped the first seven years of our group. But no worries, the quMercury project made it into the community input for the European Strategy for Particle Physics Update!

We'll have the DPG Spring Meeting¹⁰ coming up next week, with around 1600 AMO folks coming to Bonn. We will be contributing 6 talks and 7 posters, so watch out for the Quantum Metrology logo! We will offer lab tours on Tuesday, Wednesday, and Thursday at 2 pm and 5 pm, starting from the main entrance of the Physics Institute at Nussallee 12. Get in touch with us if you want to see the labs and learn more about our work. A big THANK YOU goes to Sebastian Hofferberth an his team for organizing the conference. 

In German, there is a saying "Am Aschermittwoch ist alles vorbei", which might be translated as "Everything ends on Ash Wednesday". Keeping with this saying, David Röser had his PhD defense today (Ash Wednesday!) to finish his PhD thesis not in ashes, but with a large celebration on a beautiful sunny day. The title of his thesis reads "Spectroscopy and the Path to Laser Cooling of Zinc", and David indeed developed a range of components and procedures that form the foundation of our Zinc experiment. Congratulations, Dr. Röser! 

Here it is: our first publication on ring laser technology¹¹ has been published with Optics Letters! Jannik set up two schemes to lock the free spectral range of GeoRG, our largest ring laser with an arm length of 3.5 meters. A simple phase lock is sufficient to keep the perimeter length constant to within 5 nanometers.