In quantum algorithms we need to initialize the qubits at the start of our algorithm in some quantum register. Suppose that if we are working with a four qubit quantum register we can initialize the register into values such as $|0000\rangle$ or another value such as $|0101\rangle$, which means that the first and third qubits are in basis $|0\rangle$ state and the second and fourth qubits are in basis $|1\rangle$ state. Once we have initialized these qubits as such we can then proceed to apply various quantum gates on them.
My question is that in a physical quantum computer (not a simulator) where say we represent qubits with electron spin, how do we manupulate such electrons so that we can initialize a Quantum register, say with the value $|0101\rangle$?