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In the recent years, reversible logic has emerged as a promising technology having its applications in low power CMOS, quantum computing, nanotechnology, and optical computing. The classical set of gates such as AND, OR, and EXOR are not reversible. This paper proposes a new 4 * 4 reversible gate called "TSG" gate. The proposed gate is used to design efficient adder units. The most significant aspect of the proposed gate is that it can work singly as a reversible full adder i.e reversible full adder can now be implemented with a single gate only. The proposed gate is then used to design reversible ripple carry and carry skip adders. It is demonstrated that the adder architectures designed using the proposed gate are much better and optimized, compared to their existing counterparts in literature; in terms of number of reversible gates and garbage outputs. Thus, this paper provides the initial threshold to building of more complex system which can execute more complicated operations using reversible logic.I.

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Reversible logic has shown potential to have extensive applications in emerging technologies such as quantum computing, optical computing, quantum dot cellular automata as well as ultra low power VLSI circuits. Recently, several researchers have focused their efforts on the design and synthesis of efficient reversible logic circuits. In these works, the primary design focus has been on optimizing the number of reversible gates and the garbage outputs. The number of reversible gates is not a good metric of optimization as each reversible gate is of different type and computational complexity, and thus will have a different quantum cost and delay. The computational complexity of a reversible gate can be represented by its quantum cost. Further, delay constitutes an important metric, which has not been addressed in prior works on reversible sequential circuits as a design metric to be optimized. In this work, we present novel designs of reversible sequential circuits that are optimized in terms of quantum cost, delay and the garbage outputs. The optimized designs of several reversible sequential circuits are presented including the D Latch, the JK latch, the T latch and the SR latch, and their corresponding reversible master-slave flip-flop designs. The proposed master-slave flip-flop designs have the special property that they don't require the inversion of the clock for use in the slave latch. Further, we introduce a novel strategy of cascading a Fredkin gate at the outputs of a reversible latch to realize the designs of the Fredkin gate based asynchronous set/reset D latch and the master-slave D flip-flop. Finally, as an example of complex reversible sequential circuits, the reversible logic design of the universal shift register is introduced. The proposed reversible sequential designs were verified through simulations using Verilog HDL and simulation results are presented.

Quantum-dot cellular automata (QCA) is an emerging field-coupled nanotechnology that promises to outperform existing CMOS technology. Single-layer QCA designs of full adder, full subtractor, ripple carry adder, and ripple borrow subtractor is proposed. The proposed designs are improved over both existing single-layer designs and multilayer designs.

In the recent years, reversible logic has emerged as a promising technology having its applications in low power CMOS, quantum computing, nanotechnology, and optical computing

IEEE 754r is the ongoing revision to the IEEE 754 floating point standard and a major enhancement to the standard is the addition of decimal format. This paper proposes two novel BCD adders called carry skip and carry look-ahead BCD adders respectively. Furthermore, in the recent years, reversible logic has emerged as a promising technology having its applications in low power CMOS, quantum computing, nanotechnology, and optical computing. It is not possible to realize quantum computing without reversible logic. Thus, this paper also paper provides the reversible logic implementation of the conventional BCD adder as the well as the proposed Carry Skip BCD adder using a recently proposed TSG gate. Furthermore, a new reversible gate called TS-3 is also being proposed and it has been shown that the proposed reversible logic implementation of the BCD Adders is much better compared to recently proposed one, in terms of number of reversible gates used and garbage outputs produced. The reversible BCD circuits designed and proposed here form the basis of the decimal ALU of a primitive quantum CPU.