In our experiments, we generate arrays of up to 50 optical tweezers arranged in arbitrary two-dimensional geometries, each containing a single cold atom, and separated by distances of a few micrometers. This is achieved by active sorting of atoms in larger arrays that are initially loaded stochastically . By exciting the atoms to Rydberg states (with principal quantum numbers in the range 50–100), we can induce strong, tunable dipolar interactions between the atoms .
This system is an ideal platform for the quantum simulation of spin Hamiltonians. By using van der Waals interactions we can implement the quantum Ising model in a transverse field and observe the dynamics of the magnetization and of correlation functions following a quantum quench . Using resonant dipole-dipole interactions, we observed the propagation of a spin excitation in a minimalistic spin chain governed by the XY Hamiltonian [4,5].