**Input:** $N$ ($N \ge 1$) qubits in the $\ket{0 \dots 0}$ state (stored in an array of length $N$).

**Goal:**  Change the state of the qubits to the GHZ state $\frac{1}{\sqrt{2}} \big (\ket{0\dots0} + \ket{1\dots1}\big)$.