O'Hare is a dark-matter phenomenologist whose work sits unusually close to instrumentation: he is the principal theorist of the 'neutrino fog' that limits direct-detection experiments, of directional dark matter detection (using the daily modulation of the WIMP wind to distinguish signal from background), and of the axion and ultralight dark-matter searches that increasingly rely on quantum sensors — haloscopes, comagnetometers, NMR-based searches and atomic magnetometers. He writes the sensitivity projections that tell experimentalists which quantum sensor to build. Positioned against the established body of NV-ensemble quantum sensing work — DEER, nanoscale NMR and T1 relaxometry protocols operating at pT/sqrt(Hz) field sensitivity — the axion/ALP search programme he works on consumes spin-ensemble magnetometry directly: CASPEr-class experiments are, in effect, precision NMR magnetometers operating far below pT/sqrt(Hz), and his phenomenology sets the sensitivity targets they aim at. Theory PI with strong experimental engagement.
Pop's group builds superconducting quantum circuits from high-kinetic-inductance materials, above all granular aluminium, and uses them as detectors. The distinctive capability is single-microwave-photon detection and QND photon counting with superinductor-based devices -- an extremely low dark-count, quantum-limited receiver in the GHz band -- plus fluxonium-type qubits, quantum-limited and travelling-wave parametric amplification, and studies of quasiparticle and noise mechanisms that set coherence limits. The direct sensing payoff is dark-matter search: a photon counter that beats the standard quantum limit lets a haloscope integrate far faster than an amplifier-based readout. Relative to the established NV-ensemble quantum-sensing playbook (DEER, nanoscale NMR, T1 relaxometry at pT/sqrt(Hz) ensemble sensitivity), this is the microwave/superconducting counterpart to an NV ensemble -- same objective (detect an absurdly weak field), different physical platform and roughly opposite temperature regime. A recent addition to Stuttgart's 1st Institute of Physics, so the lab is being built out now, which usually means unusual latitude for a postdoc.
Salemi builds millikelvin-scale microwave-cavity and quantum-sensor-read-out haloscopes to search for axion dark matter, relying on near-quantum-limited amplifiers to detect the vanishingly small signals expected from axion-photon conversion in a magnetic field. The lab is actively recruiting postdocs.