  We show that given two arbitrary states $\ket{\psi},\ket{\phi}$ it is
impossible to compute the transformation: $ \ket{\psi}\ket{\phi} \mapsto
\ket{\psi}\left( \mathbb{I} - 2 \ket{\psi}\bra{\psi} \right)\ket{\phi} $ The
contradiction of the existence of such operator follows by showing that using
it, two players can compute the disjoints of their sets in a single round and
$O\left( \sqrt{n} \right)$ communication complexity, which shown by Braverman
to be impossible \cite{Braverman}.
