Develops quantum metrology for ultra-weakly-coupled dark sectors and fundamental physics. Directions: (1) axion dark matter detection using entangled probe state preparation and superconducting qubit QND readout (HAYSTAC, ADMX); (2) dark radiation/energy detection with Cooper-pair box quasiparticle sensors; (3) GW detectors based on high-B-field microwave cavities probing early-universe phase transitions; (4) emergent gauge symmetries in quantum spin liquids. Co-PI DARPA QuSeN (quantum sensing of neutrinos, 2025). Devices/Sensors lead, DOE Quantum Science Center.

Prof. Figueroa-Feliciano leads Northwestern's experimental program in quantum sensing for particle physics. Key directions: (1) SuperCDMS SNOLAB — Northwestern's NU's role in the Super Cryogenic Dark Matter Search at SNOLAB (2 km underground in Canada), using ultra-pure Si and Ge crystals with superconducting TES sensors to detect low-mass dark matter (particles below the proton mass); in March 2026 the experiment reached operating temperature (<10 mK), transitioning to detector calibration for the first ever dark matter search at the site; (2) NEXUS facility at Fermilab: Northwestern-built test facility led by Figueroa-Feliciano for SuperCDMS detector calibration and for measuring how ionizing radiation affects superconducting qubits (published fall 2025); (3) Qubit-based quantum sensing: developing HVeV R&D devices with <1 eV resolution and qubit parity-detection techniques for eV-scale and sub-eV dark matter detection. Associate Vice President for Research at Northwestern; INQUIRE Executive Committee. Joint appointment at Fermilab.