Charging characteristics of a few electron triple lateral quantum dot system in GaAs/AlGaAs

We report the first experimental realization of a semiconductor triple quantum dot system in a few electrons regime. Charging properties of this "artificial tri-atom" are studied using non-invasive charge detection technique. The most fundamental configuration was initialized in which a single electron is shared resonantly between the three dots and also equivalent arrangements involving two or three electrons. Using gates we are able to tune through the quadruple points, a unique feature of triple dot systems. At a quadruple point the quantum states in all three dots resonantly coincide with each other and with the chemical potential of the leads. Unexpectedly, novel charge re-arrangement lines were observed in vicinity of quadruple points. The observed charge re-arrangement can be viewed as a basic realization of quantum cellular automata in the few electron regime. Such phenomenon may be expected for all multiple quantum dot systems greater than two, in which a change in the state of one dot may instantaneously trigger a charge rearrangement of the system. The results may lead to new opportunities for fundamental physics research and for other applications, e.g. quantum computing.