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Controlled evolution between the two states |0〉and |1〉is obtained by applying resonant microwaves to the system, but state control can also be achieved with a fast DC pulse of high amplitude.
If the appropriate pulse widths are chosen, the NOT operation ( spin flip ) can be established as
|0〉→ |1〉; |1〉→ |0〉 ( 1 )
or the Hadamard transformation ( preparation of a superposition ) can hold as
|0〉→ （|0〉＋ |1〉）/ √2 ; |1〉→ （|0〉− |1〉）/ √2 ( 2 )
