Stefan Schäffer leads the Quantum Metrology group at NBI together with Jörg Müller. Research focuses on superradiant strontium lasers: (1) quasi-continuous superradiant lasing with sub-natural linewidth; (2) Ramsey spectroscopy enhanced by cavity sub-to-superradiant phase transitions for improved atomic clock sensing; (3) continuous atom beam for Dicke-effect-free superradiant interrogation. Key work published in PRL (2023) and Nature Communications (2024). Part of EU iqClock and ESA collaborations.

Quantenbit operates segmented micro-structured Paul traps for scalable trapped-ion quantum information and, increasingly, for quantum sensing. Directions: (i) trapped Rydberg ions -- combining the tight confinement of a Paul trap with the giant polarizability of Rydberg states, which is simultaneously a fast-gate resource and an extremely sensitive electric-field probe; (ii) motional-mode sensing of electric fields and surface noise; (iii) deterministic single-ion implantation, where a cold ion is extracted from the trap and implanted with nm-scale placement -- directly relevant to building NV/donor arrays with known ion counts, and to single-ion detection validation; (iv) TACTICa, applying ion-trapping and quantum-logic spectroscopy to 229Th toward a nuclear clock; (v) single-atom heat engines and quantum thermodynamics. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), the deterministic-implantation line is the natural upstream complement: it is the route to engineering NV ensembles/arrays with controlled density rather than relying on stochastic implantation. Strong local coupling to Budker (Th-229, exotic physics) and Wendt (laser ionization).

PREFERRED. Vuletic's group generates large-scale spin squeezing and entanglement in cold and ultracold atomic ensembles to push optical atomic clocks and rotation/field sensors below the standard quantum limit, alongside work on cavity QED, Rydberg tweezer arrays, and nonlinear quantum optics at the single-photon level. Recent work includes cavity-feedback spin squeezing for ytterbium clocks and fault-tolerant neutral-atom quantum sensor/processor arrays with collaborators at Harvard.

The LARISSA group develops multi-step resonance ionization laser spectroscopy and RIMS: element- and isotope-selective laser ionization used both as an ultratrace analytical technique (actinide detection at extreme selectivity, environmental and nuclear-forensic samples) and as a spectroscopy tool for exotic and short-lived isotopes, feeding ion-source development for facilities such as ISOLDE/CERN. A major current thrust is the atomic and ionic spectroscopy of thorium, including the 229mTh isomer that underpins the nuclear-clock effort, done jointly with Schmidt-Kaler's trap group and Duellmann's nuclear chemistry. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), the transferable capability here is selective, quantum-state-resolved detection of single atoms/ions -- the readout problem, approached spectroscopically rather than magnetically.