Introduction to Quantum Computing
Each electron spin can either be pointed up – the “spin-up" state |↑> – or it can be pointed down, – the “spin-down state |↓>."
As qubits, they can also be in superpositions states of |↑> and |↓>.
An equal superposition of these configurations results in four complex probability amplitudes (weighting factors) ci:
A π-pulse applied to the first qubit (left-most spin in the bra-ket) will flip its spin. This rotation is implemented using an electromagnetic pulse with a precise amplitude and duration such that it rotates the spin by 180 degrees.
A single π-pulse on a single qubit effectively shuffles the individual probability amplitudes amongst all of the 2N = 4 spin configurations making up a quantum superposition state.
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