The fundamental method for computing is majority gate or majority voter method  .
The majority gate produces an output that reflects the majority of the inputs.
The fundamental logic structure of QCA is the 3-input majority gate.
The structure has four inputs (two inputs and their inversion) and one output, figure 5 shows the QCA structure constructed using QCAdesigner tool, the main advantage of QCA technology is availability of inputs and their inversion simultaneously (90[degrees] and 45[degrees] rotation of cell in a single QCA wire) hence simple two input majority gate being constructed with control inputs +1 and -1.
Inputs are divided such that inverted inputs a' and b' forms right side majority gate with clock 0 and a,b is at left side majority gate with clock 0.
The advantage of the circuit considered in figure 10 is two different majority gates evaluated independently and the middle gate is used to get the output, there by reducing the one majority gate evaluation time and also separate clock being applied tot the middle output gate and hence the error (unploarization state of electron) due to clocking being reduced.
At clock 0 inputs are available for comparator; clock 1 is used to carry information for majority gate, clokc2 and 3 for evaluating the majority logic.
This paper presents a quantum dot cellular automata complex gate composed of 3 input and 7 input majority gates to represent complex logic gates.