Abstract: High-precision and -sensitivity measurements of energy and momentum conservation in weak nuclear decay are powerful, model-independent probes of new physics from the eV to TeV scale. In these studies, we focus on ​“smoking gun” signatures of physics beyond the standard model (BSM) – particularly in the lepton sector where the SM has already been broken (non-zero neutrino mass). These experiments range from using rare-isotope-doped superconductors to precisely measure the eV-scale nuclear recoils from the momentum ​“kick” that a single daughter atom gets from a neutrino in beta decay, to constructing a tonne-scale liquid xenon time-projection-chamber deep in an active nickel mine in Canada to search for neutrinoless double beta decay with half-lives that are more than 15 orders of magnitude longer than the age of our universe. 

In this talk, I will discuss both of these topics, with a focus on our new work using rare-isotope-doped superconductors to directly measure nuclear decay recoils which carry signatures of weakly coupled BSM physics, including neutrino mass, exotic weak currents, and potential ​“dark” particles. Since these recoils are encoded with the fundamental quantum information of the decay process, they also provide a unique probe of nuclear/neutrino entanglement, decoherence, and quantum localization in radioactive decay. Finally, I will discuss our future prospects of using macroscopic amounts of harvested rare isotopes in optically levitated femtogram spheres for direct decay-by-decay momentum measurements using quantum-limited sensing techniques.