Nulling a cell of a complex matrix is described. A complex matrix and a modified Givens rotation matrix are obtained for multiplication by a processing unit, such as a systolic array or a CPU, for example, for the nulling of the cell to provide a modified form of the complex matrix. The modified Givens rotation matrix includes complex numbers c*, c, −s, and s*, wherein the complex number s* is the complex conjugate of the complex number s, and wherein the complex number c* is the complex conjugate of the complex number c. The complex numbers c and s are associated with complex numbers of the complex matrix including the cell to be nulled. The modified form is then output by the processing unit. The modified Givens rotation matrix may be implemented as a systolic array or otherwise used for processing complex numbers or matrices.