We now look at the construction of a single-qubit quantum computer (hypothetical):

We encode the qubit using the excitation of an electron.
We assume that an electron has only states $\ket{0}$ and $\ket{1}$ with 0 being the ground state.
The states have energy levels $\pi$ and $2\pi$.

Now we need to be able to do 3 things:
1. Initialize qubit with $\ket{0}$, also called cooling.
2. Ability to measure the qubit.
3. Ability to apply a unitary to qubit.

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