Superradiant Interactions of Cosmic Relics

Cosmic relics such as the cosmic neutrino background (CvB) are among the most compelling and elusive targets in fundamental physics. With conventional detectors, the interaction rate is so small that a 10-cm sphere of matter would see fewer than one event over the age of the universe. I will describe a framework in which this changes dramatically when macroscopic targets are prepared in simple quantum product states, as in NMR spin ensembles. In this regime, inelastic transitions of the target’s internal state can exhibit superradiant enhancements: the rate scales as N² with the number of constituents, boosting the CvB rate for a 10-cm sphere by ~20 orders of magnitude to ~1 Hz. I will present representative rates and discovery opportunities for relic neutrinos, axion and dark-photon dark matter, and local neutrino sources (reactor and solar), and explain why thermal-neutron scattering on NMR samples offers a natural first testbed for the needed quantum protocols. Finally, I will show how superradiant interactions appear as correlated noise on the target, motivating quantum observables beyond traditional energy-exchange measurements.

Speaker: Savas Dimopoulos, Stanford University