**Input:** Two qubits (stored in an array of length 2) in an arbitrary two-qubit state ${\color{blue}\alpha} |00\rangle + {\color{blue}\beta} |01\rangle + \gamma |10\rangle + \delta |11\rangle$.

**Goal:**  Change the two-qubit state to ${\color{red}\beta} |00\rangle + {\color{red}\alpha} |01\rangle + \gamma |10\rangle + \delta |11\rangle$.

> This task can be solved using one library function; as an exercise, try to express the solution using several (possibly controlled) Pauli gates.  