= Solution
The required <superposition> is the <Bell state>
$$
\frac{|++\rangle+|--\rangle}{\sqrt2}
=\frac{|00\rangle+|11\rangle}{\sqrt2}=|\Phi^+\rangle.
$$
\b[Prepare $|00\rangle$, apply $H$ to the first <qubit>, then apply CNOT from the first to the second.] The intermediate state is $(|00\rangle+|10\rangle)/\sqrt2$, and the <controlled-NOT gate> gives the required <Bell state>. No final basis change is needed: the two displayed expressions represent exactly the same <vector>.
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