James K. Thompson describes how photons repeatedly reflected inside an optical cavity can couple laser-cooled atoms. These collective interactions provide tools for both simulating many-body systems and improving precision measurements. The seminar examines ways to shape the coupling, including exchange and XYZ interactions, interactions involving three or four particles, dissipative processes and protection of coherence through a many-body energy gap. Applications include studying time-dependent phases of superconductors, increasing the sensitivity of matter-wave interferometers and advancing optical clocks. The organizer provides both an Ann Arbor venue and an online attendance option.

Sahand Tabatabaei presents SQUINT, a sensing platform that combines molecular electron spins, sensitive mechanical detection and control of spin interactions. Molecular sensors can be chemically adjusted and positioned near targets, offering flexibility that defects fixed inside a solid host cannot provide. The work uses a modified XYXY decoupling sequence to reduce dipolar interactions despite uneven control fields. In a sample containing roughly 100 trityl radicals, the reported coherence time reaches about 400 microseconds. These longer-lived spins enable frequency-selective measurements of weak alternating magnetic fields and spectroscopy of nearby nuclear-spin ensembles. The seminar explores how molecular control and mechanical readout can bring quantum sensing closer to complex chemical targets.