Ex7 6

$\def\abs#1{|#1|}\def\i{\mathbf {i}}\def\ket#1{|{#1}\rangle}\def\bra#1{\langle{#1}|}\def\braket#1#2{\langle{#1}|{#2}\rangle}\def\tr{\mathord{\mbox{tr}}}\mathbf{Exercise\ 7.6}$

Show directly that, in the distributed computation algorithm of section 7.5.4, when $u = v$, $\abs{\braket{x,y}{\psi}}^2 = 0$ for all $x \ne y$.