  We present a theoretical proposal of a tunable charge qubit, hosted in triple
quantum dots. The manipulation is solely performed by changing the heights of
the two potential barriers between the three dots, while the energy of all
three dots are fixed. We have found that when the relative height of the two
barriers are changed, the direction of the axis of rotation in performing
single-qubit gates can be varied. On the other hand, the corresponding rotation
speed can be tuned by raising or lowering the two barriers at the same time.
Our proposal therefore allows for tunability of both the rotation axis and
rotating speed for a charge qubit via all-electrical control, which may
facilitate realization of quantum algorithms in these devices.
