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IOP Publishing

Quantum Computing

A pathway to quantum logic design

Hafiz Md Hasan Babu

Chapter 6

Quantum adder circuits

Several types of adders are used in computing systems, such as carry skip adders (CSAs), binary coded decimal (BCD) adders, and so on. Among them the most common is the ripple carry adder, in which full-adders are connected in series and carry is propagated through all the stages and hence requires more carry propagation time to generate the carry output. Carry look ahead adders are the fastest of all the adders since the carry output is generated in parallel computation, but this requires a large number of gates. The CSA is the most promising adder which presents a compromise between hardware and performance compared to both adders mentioned above. In the full-adder operation, if either of the inputs is a logical one, then the cell will propagate the carry input to the carry output. Hence the i