Buechler leads quantum many-body theory at ITP III: strongly interacting quantum systems, quantum optics, and the theory of cold atomic and molecular gases -- in particular Rydberg systems, where he has been a central theorist for interaction-engineered tweezer arrays, dressed interactions and photon-photon interactions in Rydberg media. He is the theory counterpart to Pfau's and Wrachtrup's experiments in the same department. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), a theory-first inclusion: the relevant output is the protocol layer -- how to engineer Hamiltonians in interacting spin/Rydberg ensembles so that entanglement or dressing improves sensitivity beyond the standard quantum limit, which is exactly the theory an NV-ensemble sensing programme needs and rarely has in-house.
Hong runs Hybrid Optical Quantum Technologies within Stuttgart's FMQ institute: optomechanical and opto-mechanical-spin hybrid devices used for quantum sensing and for tests of quantum mechanics at larger mass scales. Work covers cavity/phononic-crystal optomechanics driven toward the quantum regime (ground-state cooling, back-action-evading and quantum-limited displacement/force readout) and the coupling of diamond spin defects to mechanical motion, including levitated-diamond spin-mechanics -- where an NV inside a levitated particle both senses and controls the particle's motion. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), this is the same colour-centre physics, deliberately hybridized with mechanics: the sensing target shifts from magnetic field to force, acceleration and displacement, and the group sits alongside Wrachtrup's NV programme in the same building, which is a considerable practical advantage.
van Slageren's group is one of the leading molecular-qubit labs. They synthesize their own paramagnetic molecules, characterize them with a wide spectroscopic and magnetometric arsenal (multi-frequency and high-field EPR, pulsed EPR/DEER, THz spectroscopy, SQUID magnetometry) and back it with ab-initio calculation. Landmarks include room-temperature quantum coherence in a copper(II) molecular qubit, quantitative prediction of nuclear-spin-diffusion-limited coherence times, measurement of coherence in thin films without post-processing, and recent observation of a sizeable spin-electric effect -- electric-field control of a molecular spin state, which is the mechanism you would exploit for a molecular electrometer. Current direction: molecular quantum spintronics, marrying organic spintronics to molecular magnetism. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), this is the molecular alternative to the diamond defect: chemically tunable spin qubits whose coherence can be engineered by ligand design rather than by host-crystal purification. Immediate neighbours are Krueger (nanodiamond chemistry) and Wrachtrup (NV readout), both already on file -- an unusually complete local ecosystem.