Quantum full adder is the basic elements of quantum computers

in order to reduce the energy loss and cut the construction cost and the difficulty of physical realization. The paper proposes a new type of

n

-bit quantum full adder which uses 3

n

CNOT(Controlled NOT) Gates and 2

n

-1 Toffoli gates to implement

n

-bit quantum addition and subtraction

adopts the carry look-ahead mode without carry input

and judges the carry of addition and positive and negative sign of subtraction with the highest overflow mark bit that does not participate in the calculation of high and low bit

which does not increase time delay of the circuit and suits for

n

-bit quantum parallel operation. The simulation operation with random number of 4

8

16 and 32 di

gits verifies the correctness of the full adder separately. The low quantum cost and simple circuit structure of the quantum full adder is helpful to improve the size and integration of integrated circuits.