**Inputs:**

1. A non-negative real number $\alpha$.
2. A non-negative real number $\beta = \sqrt{1 - \alpha^2}$.
3. A real number $\theta$.
4. A qubit in state $|0\rangle$.

**Goal:** Transform the qubit into state $\alpha|0\rangle + e^{i\theta}\beta|1\rangle$.

> Since only the relative amplitudes and relative phase have any physical meaning, this allows us to prepare any single-qubit quantum state we want to.