It's either on or off, open or closed. It can't be something in between. But in the quantum world, a particle can be every possible combination of the two states. It's neither 1 nor 0. Quantum reality creates a serious problem, however.
Observation draws the qubit out of the quantum world.
It becomes either a 1 or a 0. And your computation is blown. In conventional computing, this so-called process of error correction can be done by pushing a bit back in the right direction if it gets flipped the wrong way. Quantum computing skeptic Rolf Landauer, a researcher at IBM in New Jersey, three years ago asserted that no one would ever figure out how to do quantum error correction. He acknowledges that he was impressed when Shor proposed a way to do so.