We show that n thermal fermionic alkaline-earth-metal atoms in a flat-bottom trap allow one to robustly implement a spin model displaying two symmetries: the S n symmetry that permutes atoms occupying different vibrational levels of the trap and the SU(N ) symmetry associated with N nuclear spin states. The symmetries make the model exactly solvable, which, in turn, enables the analytic study of dynamical processes such as spin diffusion in this SU(N ) system. We also show how to use this system to generate entangled states that allow for Heisenberg-limited metrology. This highly symmetric spin model should be experimentally realizable even when the vibrational levels are occupied according to a high-temperature thermal or an arbitrary nonthermal distribution.DOI: 10.1103/PhysRevA.93.051601The study of quantum spin models with ultracold atoms [1,2] promises to give crucial insights into a range of equilibrium and nonequilibrium many-body phenomena from quantum spin liquids [3] and many-body localization [4] to quantum quenches [5][6][7] and quantum annealing [8]. While other approaches exist [9][10][11][12], the most common approach taken to implement a quantum spin model with ultracold atoms relies on preparing a Mott insulator in an optical lattice, where the internal states of atoms on each site define the effective spin [1,[13][14][15][16][17][18][19]. Virtual hopping processes to neighboring sites and back then give rise to effective superexchange spin-spin interactions. Since the superexchange interactions are typically very weak ( kHz) [1] (unless the traps are operated near surfaces, which can reduce spacings and increase energy scales [20][21][22]), it is a significant challenge in experimental cold-atom physics to achieve temperatures and decoherence rates low enough to access superexchange-based quantum magnetism.Since ultracold atoms can be prepared in specific internal (i.e., spin) states with extremely high precision, spin temperatures that can be realized are much lower than the experimentally achievable motional temperatures. It is therefore tempting to circumvent the problem of high motional temperature by constructing a spin model in such a way that the motional and spin degrees of freedom are effectively decoupled. We provide a recipe for such a decoupling and hence for realizing spin models with thermal atoms.The first crucial ingredient for implementing such a spin model is to depart from second-order superexchange interactions and use contact interactions to first order [23][24][25][26][27][28][29][30][31][32]. As shown in Fig. 1(a), this can be achieved if all atoms sit in different orbitals of the same anharmonic trap and remain in these orbitals throughout the evolution, which is a good approximation for weak interactions [23][24][25]30,31]. In that case, the occupied orbitals play the role of the sites of the spin Hamiltonian. However, because of high motional temperature in such systems, every run of the experiment typically yields a different set of populated orbitals and hence a diff...