Reversible Logic as a Stepping Stone to Quantum Computing

Huidong Li

Shaveta Thakral, Dipali Bansal

Increasing miniaturization and demand of low power electronics is highly motivating research on reversible logic. Reversible logic has attracted signification attention in fields of Low power VLSI design, computer graphics, quantum computing and communication. A lot of work has been done on synthesis and optimization of reversible circuits followed by quantitative analysis on various optimization metrics like ancillary inputs, garbage outputs and quantum cost. It is therefore obvious to present a quick guide on reversible logic implementation to bridge gap between theory and implementation. Taxonomy diagrams of work done in reversible logic domain are also presented to give a quick review of all about reversible logic. Quantum realization of popular reversible Fredkin gates using RCViewer tool is also presented which will be stepping stone for a new researcher to synthesize and optimize any complex reversible logic based circuit.

Saleem Mohammed Ridha Taha

Sadia Afrin, Fahim Shihab Shan, Zarrin Tasnim Sworna

Reversible logic is one of the stepping stones in low power circuit design. Due to low power consumption and minimum bit loss features, future quantum computing devices are estimated to be reversible. Compared to addition, multiplication is a step further in the ladder of abstraction. It is the manifestation of a pattern generation system capable of representing 3-D patterns and transforming them by rotation, projection, reflection etc. The use of reversible logic in this field can reduce the wastage of energy, power and improve many factors. In this paper, an efficient multiplication algorithm has been proposed which is a modification of conventional shift-and-add multiplication method. Implementing proposed algorithm two reversible multiplier circuit has been proposed. For producing partial product, Peres gate has been used for the first design and Toffoli gate for the second design. Both of the circuits use Peres gate as Half-Adder and HNG gate as Full-Adder for addition of partial products. The first design is improved radically in terms of quantum cost, delay and the second design is notably improved in terms of transistor count and hardware complexity compared to the existing best known multipliers.

Hafiz Md. Hasan Babu

G.Lakshmi Bharath2 A.Bhavana1

Programmable reversible logic is emerging as a prospective logic design style for implementation in modern nanotechnology and quantum computing with minimal impact on circuit heat generation. Recent advances in reversible logic using and quantum computer algorithms allow for improved computer architecture and arithmetic logic unit designs. In this paper, a 2*2 Swap gate which is a reduced implementation in terms of quantum cost and delay to the previous Swap gate is presented. Next, a novel 3*3 programmable UPG gate capable of calculating the fundamental logic calculations is presented and verified, and its advantages over the Toffoli and Peres gates are discussed. The UPG is then implemented in a reduced design for calculating n-bit AND, nbit OR and n-bit ZERO calculations. Then, two 3*3 RMUX gates capable of multiplexing two input values with reduced quantum cost and delay compared to the previously existing Fredkin gate is presented and verified. Next, 4*4 reversible gate is presented and verified which is capable of producing the calculations necessary for two-bit comparisons. The UPG and RC are implemented in the design of novel sequential and tree-based comparators. Then, two novel 4*4 reversible logic gates (MRG and PAOG) are proposed with minimal delay, and may be configured to produce a variety of logical calculations on fixed output lines based on programmable select input lines. A 5*5 structure (MG) is proposed that extends the capabilities of both the MRG and PAOG. The comparator designs are verified and its advantages to previous designs are discussed. Then, reversible implementations of ripple-carry, carry-select and Kogge-Stone carry look-ahead adders are analyzed and compared. Next, implementations of the Kogge-Stone adder with sparsity-4, 8 and 16 were designed, verified and compared. The enhanced sparsity-4 Kogge-Stone adder with ripple-carry adders was selected as the best design, and its implemented in the design of a 32-bit arithmetic logic unit is demonstrated. The proposed ALU design is verified and its advantages over the only existing ALU design are quantitatively analyzed.