Fig. 1

Schematic of the system. The experimental system consists of paramagnetic colloids placed via optical tweezers in lithographic double wells arranged along the edges of a square lattice. Each colloid is gravitationally trapped in one microgroove, and it can sit in one of the two wells. A perpendicular field B magnetizes the colloids, thus introducing a repulsive dipolar interaction. The edges of the square lattice can be decimated by simply removing the colloids from the corresponding microgrooves (dashed green rectangles). Red and blue glows denote positive and negative topological charges, respectively