McDonald leads the Quantum Technologies for Fundamental Physics (QTFP) theme at CQSE Manchester. Research directions: (1) Manchester Axion Novel Cavity eXperiment (MANCX) — building a cavity haloscope to search for QCD axions and axion-like particles coupling to photons via resonant microwave cavity enhancement at Manchester; (2) Astroparticle theory — superradiance from black holes for ultralight dark matter/axion bounds; neutron star probes of new physics; (3) Dark energy / extended gravity — vacuum energy and Casimir-type effects; (4) High-frequency gravitational waves — novel detection concepts. Workshop chair for Manchester's QTFP international workshop (Jan 2026). Interdisciplinary collaboration with quantum engineers, low-temperature physicists, and particle physicists.

Works on quantum-limited sensing for astroparticle physics. Directions: (1) Pierre Auger Observatory — UHE cosmic ray composition and spectrum via radio and fluorescence detection; (2) liquid argon dark matter detectors; (3) co-PI DARPA QuSeN (2025) — quantum sensing of neutrinos using phonon-coupled SC qubit sensors with Cleland and Chou. KICP member.

Builds radio and mm-wave quantum-limited sensing instruments for high-energy astrophysics and cosmology. Directions: (1) PUEO — balloon-borne radio Cherenkov (Askaryan) detector for ultra-high-energy cosmogenic neutrinos; (2) RNO-G — ground-based radio neutrino array at Summit Station, Greenland; (3) UHE cosmic ray radio detection methodology; (4) CMB instrumentation (BICEP/Keck, SPT, CMB-S4). 2025 APS Fellow; 2022 Moore EPII award. Director KICP.

Experimental astroparticle physicist developing radio-based detection of ultra-high-energy cosmic rays. Directions: (1) HAWC — high-altitude water Cherenkov detector for gamma-ray and cosmic ray sensing; (2) IceTop surface array at IceCube for cosmic ray composition at the knee; (3) radio detection of cosmic-ray-induced air showers (Askaryan emission) as a technique for large-scale UHE cosmic ray sensing. Enrico Fermi Institute member.