For their experiment, the Delft team bent a carbon nanotube into a "U" shape and put two electrons on the surface. They used electrons because the information that describes the state of an electron's spin, whether it's pointing up or down, is one kind of qubit. (There are others, but for simplicity's sake, we'll stick with electron and spin). They limited the number of electrons to two because it would have been harder to see the spin state of only one, while three would have been more difficult to control.
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Next, the scientists showered the nanotube in an electric field, rapidly switching from positive to negative, to spiral the electrons up and down the tube, inside and out. A positive field made the electrons move in one direction and a negative one forced them in the opposite direction.
When the electrons encountered the "U" bend, they flipped over into another spin state, either from up to down or from down to up. That's because the curve pinched the electric field and made it uneven. The electron flip was the equivalent of turning a switch in a transistor from on to off or from off to on, essentially making a 0 or 1.