Advances with trapped ultracold atoms intensified interest in simulating complex physical phenomena, including quantum magnetism and transitions from itinerant to non-itinerant behavior.Here we show formation of antiferromagnetic ground states of few ultracold fermionic atoms in single and double well (DW) traps, through microscopic Hamiltonian exact diagonalization for two DW arrangements: (i) two linearly oriented one-dimensional, 1D, wells, and (ii) two coupled parallel wells, forming a trap of two-dimensional, 2D, nature. The spectra and spin-resolved conditional probabilities reveal for both cases, under strong repulsion, atomic spatial localization at extemporaneously created sites, forming quantum molecular magnetic structures with non-itinerant character. These findings usher future theoretical and experimental explorations into the highly correlated behavior of ultracold strongly repelling fermionic atoms in higher dimensions, beyond the fermionization physics that is strictly applicable only in the 1D case. The results for four atoms are well described with finite Heisenberg spin-chain and cluster models. The numerical simulations of three fermionic atoms in symmetric DWs reveal the emergent appearance of coupled resonating 2D Heisenberg clusters, whose emulation requires the use of a t-J-like model, akin to that used in investigations of high T c superconductivity. The highly entangled states discovered in the microscopic and model calculations of controllably detuned, asymmetric, DWs suggest three-cold-atom DW quantum computing qubits. New J. Phys. 18 (2016) 073018 C Yannouleas et al New J. Phys. 18 (2016) 073018 C Yannouleas et al ⎟ ⎟ ⎟ 18 J J J t t t J J J J t t t J J J J t t t t t t J J J t t t J J J J t t t J J J J Figure B1. Schematics indicating the four-site numbering convention in the Heisenberg Hamiltonian. (a) The case of formation of a rectangular parallelogram (ring topology). The Heisenberg exchange parameters = = J J s 14 23 and = = J J r 12 34 . (b) The linear arrangement of the four sites which results from (a) by opening the ring through setting = J 0 34 , = J r 12 , = = J J s 14 23 . ( ) Due to the reflection symmetry in x and y, H RP,gen has only two different exchange constants = = J J s 14 23 and = = J J r 12 34