Consider two states |ψ1> = 2i|ϕ1> + |ϕ2> - a|ϕ3> + 4|ϕ4>
and
|ψ2> = 3|ϕ1> - i|ϕ2> + 5|ϕ3> - |ϕ4>,
where |ϕ1>,
|ϕ2>, |ϕ3>, and |ϕ4>
are orthonormal kets, and where a is a constant.
Find the value of a so that |ψ1> and
|ψ2> are orthogonal.