  In submicron superconducting squares in a homogeneous magnetic field,
Ginzburg-Landau theory may admit solutions of the vortex-antivortex type,
conforming with the symmetry of the sample [Chibotaru et al., Nature 408, 833
(2000)]. Here we show that these fascinating, but never experimentally observed
states, can be enforced by artificial fourfold pinning, with their diagnostic
features enhanced by orders of magnitude. The second-order nucleation of
vortex-antivortex molecules can be driven either by temperature or applied
magnetic field, with stable asymmetric vortex-antivortex equilibria found on
its path.
