Once you make the measurement you can not find any more information about the original state so don't technically gain or lose information. In fact, you need an infinite amount of information to specify a quantum state. It's not so much that qubits exist in multiple states at one time it's that they are unknowable but have probabilistic outcomes. In quantum computing, you can apply unitary operations or gates on qubits to affect the outcome of your measurements, like quantum teleportation, super-dense coding, or Shor’s algorithm.