Text Box: Another state flip-flop completes the cycle, fully restoring the original unknown state. Text Box: The second undoing measurement is identical to the first, shifting the states back to their original position, erasing the information. Text Box: A state flip-flop exchanges up and down. Text Box: All possible quantum states of a qubit are represented on a sphere and labeled by their color. Text Box: First measurement gives some information about the unknown quantum state, accompanied by intrinsic state disturbance (all states are shifted down). Text Box: Illustration of the measurement undoing procedure applied to a superconducting phase qubit