const c = circuit(9);
// Outer phase-flip layer: copy qubit 0 onto the block leaders 3 and 6.
c.cx(0, 3);
c.cx(0, 6);
// Put each block leader into the |+> sublattice.
c.h(0);
c.h(3);
c.h(6);
// Inner bit-flip layer: expand each leader into a (|000>+|111>) block.
c.cx(0, 1);
c.cx(0, 2);
c.cx(3, 4);
c.cx(3, 5);
c.cx(6, 7);
c.cx(6, 8);
return c;