Bad Qubits — Learn Quantum by Doing

|q⟩ Bad Qubits

Multiple choice

Per this lesson, a phase-flip oracle marking item x* acts as the identity everywhere except for what change on the diagonal entry for |x*>?

It places a 0 there, erasing the marked item's amplitude
It places a -1 there, multiplying the marked item's amplitude by -1
It swaps that entry with the |0...0> entry
It places a +2 there, doubling the marked item's amplitude