Introduction to the Physics of Coherent interactions

• Angelo Esposito (Istituto Nazionale di Fisica Nucleare)

Room: Room Majorana

Superradiant interactions of cosmic relics

• Asimina Arvanitaki (Perimeter Insitute)

Room: Room Majorana Cosmic relics such as the cosmic neutrino background (CνB) are among the most compelling predictions of modern cosmology, yet they remain undetected because their interactions with ordinary matter are extraordinarily weak — a 10-cm detector would expect far less than one event over the age of the universe. I will describe a new approach in which macroscopic targets, such as spin ensembles familiar from NMR, prepared in easy to achieve quantum states can respond collectively to these tiny signals. In this regime, interactions are superradiantly enhanced, with rates scaling as the square of the number of particles in the target, boosting relic neutrino signals to the Hz level. I will discuss the broader implications for detecting relic neutrinos, axion and dark-photon dark matter, and explain why neutron beams incident on tabletop systems based on NMR techniques provide a natural testing ground. Finally, I will argue that these interactions appear not as conventional energy deposits but as correlated noise, pointing toward new detection strategies rooted in quantum measurement science.

Discussion Room: Room Majorana

Superradiant Neutrino Sources

• Benjamin Jones (University of Texas at Arlington & University of Manchester)

Room: Room Majorana Many analogies exist between neutrino physics and optics because the neutrino is a nearly massless particle whose feeble environmental interactions permit coherent quantum effects. However, it is only relatively recently that we have begun to explore the potential of quantum phenomena in neutrino physics, with neutrino oscillations and coherent elastic neutrino-nucleus scattering as prominent examples. Superradiance — which emerges from collective spontaneous emission in optically pumped gases — may also have a parallel counterpart in neutrino physics.In my talk, I will discuss some of these analogies and introduce a new — and highly speculative — concept of superradiant neutrino emission from a radioactive Bose-Einstein condensate, which could form the basis for a superradiant neutrino laser.

Experimental Investigation of Macroscopically Coherent States in Optically Excited Erbium-Doped Crystals

• Federico Chiossi (University of Padova)

Room: Room Majorana We report the experimental observation and characterization of macroscopically coherent states involving several 10¹² erbium ions in cryogenically cooled crystals. These states emerge spontaneously from an optically excited population of 10¹⁵ ions, coupled solely through their own near-infrared emission. The synchronization of the ions' dipoles accelerates their radiative decay by up to a million times, producing a powerful burst of coherent emission. Our results reveal the dynamics of large-scale coherent phenomena in solid-state ensembles and open new perspectives for exploiting such coherent states to enhance the rate of extremely rare processes through cooperative behavior.