**Inputs**:

1. A qubit in state $\ket{\psi} = \alpha \ket{0} + \beta \ket{1}$.
2. An integer $k \geq 0$.

**Goal**: 
Change the state of the qubit to $\alpha \ket{0} + \beta \cdot e^{\frac{2\pi i}{2^{k}}} \ket{1}$

> Be careful not to introduce an extra global phase! 
This is going to be important in the later exercises.