Phys.org  August 26, 2024 Spin squeezing is a form of entanglement that reshapes the quantum projection noise to improve measurement precision. An international team of researchers (USA – Harvard University, UC Berkeley, Germany) provided numerical and analytic evidence for the following conjecture: any Hamiltonian exhibiting finite-temperature easy-plane ferromagnetism could be used to generate scalable spin squeezing, thereby enabling quantum-enhanced sensing. It is based on a connection between the quantum Fisher information of pure states and the spontaneous breaking of a continuous symmetry. They demonstrated that spin squeezing exhibits a phase diagram with a sharp transition between scalable squeezing and non-squeezing […]