scaff_module cRz ( qbit ctrl, qbit target, const double angle ) {
	/* cRz identity matrix:
		[ [ 1 0 0 0 ]
			[ 0 1 0 0 ]
			[ 0 0 e^(-i*angle/2) 0 ]
			[ 0 0 0 e^(i*angle/2) ] ]
	*/

	Rz(target, angle/2);
	CNOT(ctrl, target);
	Rz(target, -angle/2);
	CNOT(ctrl, target);
	Rz(ctrl, angle/2);
}