  Superconducting rings with exactly $\Phi _0/2$ magnetic flux threading are
analogous of Ising spins having two degenerate states which can be used to
store binary information. When brought close these rings interact by means of
magnetic coupling. If the interactions are properly tailored, a system of such
superconducting rings can accomplish static quantum logic in the sense that the
states of the rings interpreted as Boolean variables satisfy the desired logic
relations when and only when the whole system is in the ground state. Such
static logic is essential to carry out the static quantum computation [1,2].
