  We show how, with the use of quantum interference, we can violate, in some
sense, the rule that charges of equal sign always repel each other. By
considering two electrons that propagate parallel to each other in a
Mach-Zehnder interferometer, we show that the quantum superposition of the
electrostatic repulsion when the electrons propagate in the same path with the
absence of interaction when they propagate in opposite paths may result in an
effective attraction between them, when we post-select by which port each
electron leaves the interferometer. We also discuss an experimental setup that
could be used to verify such an effect.
