We'll have the DPG Spring Meeting⁶ 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 technology⁷ 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.

The end of a busy week: Stefan Gessler finished and successfully defended his bachelor's thesis, congratulations! Thomas Gereons finished his internship, only to continue next week on his master's thesis project. Also, three 10th grade high school students spent the week with us: Marie, Karl, and Jonathan explored the capabilities of small Arduino boards, asking ChatGPT to generate the code required to drive small servo motors.

Anica went into mass production mode: while the previous paper has been published with Optics Letters⁸, the next one is already on the arXiv⁹. Both papers study frequency conversion in gas-filled hollow-core fibers in different regimes. Congratulations to Anica! 

With the help of Andreas Brotzer from LMU, we installed a state-of-the-art broadband seismometer in our basement. Side-by-side with our own narrowband seismometer, our tiltmeter, and the large ring laser, we embarked on a three-week measurement campaign during the Christmas break. Indeed, we were able to record a number of teleseismic events (= earthquakes on the other side of the globe) with magnitudes between M6.5 and M7. Thanks a lot to Andreas and the entire team at the Geodetic Observatory in Fürstenfeld-Bruck, as well as to Heiner Igel's group at LMU, for loan of the equipment and for support in data analysis. 

Happy New Year to all of you, hoping for a peaceful and successful year 2025! We are welcoming two new additions to the team: Thomas Gereons started his master internship with us, and Tessa Koch dived into her Bachelor's thesis: good luck to the two of you!

Ring lasers are interferometers that require length stability at a fraction of the wavelength: not a mean feat for heterolithic structures of more than 10 meter length, especially when operated in a wobbling University building with sizeable temperature fluctuations. In a new preprint¹⁰, Jannik Zenner presents two methods to stabilize the length of the 14-meter ring cavity to within a few nanometers. Congratulations to Jannik and the team!