Spin Ensembles: Collective Effects and Quantum Metrology

This lecture covers the concept of spin ensembles, focusing on their collective effects and applications in quantum metrology. Topics include Dicke states, polaritons, coherent spin states, Ramsey interferometer, quantum Fisher information, and limits to interferometry. The instructor discusses the algebraic properties of angular momentum, symmetries of Dicke states, entanglement in spin ensembles, and the bosonic nature of Dicke states. Additionally, the lecture explores the geometric interpretation of Dicke states, the rotation in Bloch space, and the symmetries of collective spins.