Scalable spin squeezing from spontaneous breaking of a continuous symmetry
Spontaneous symmetry breaking is a property of Hamiltonian equilibrium states which, in the thermodynamic limit, retain a finite average value of an order parameter even after a field coupled to it is adiabatically turned off. In the case of quantum spin models with continuous symmetry, we show that this adiabatic process is also accompanied by the suppression of the fluctuations of the symmetry generator—namely, the collective spin component along an axis of symmetry.
arXiv:2202.08607 (2022) / Phys. Rev. Lett. 129, 113201 (2022)