Fault-Tolerant Reversible Circuits

Reversible hardware computation, that is, performing logic signal transformations in a way that allows the original input signals to be recovered from the produced outputs, is helpful in diverse areas such as quantum computing, low-power design, nanotechnology, optical information processing, and bioinformatics. We propose a paradigm for performing such reversible computations in a manner that renders a wide class of circuit faults readily detectable at the circuit's outputs. More specifically, we introduce a class of reversible logic gates (consisting of the well-known Fredkin gate and a newly defined Feynman double-gate) for which the parity of the outputs matches that of the inputs. Such parity-preserving reversible gates, when used with an arbitrary synthesis strategy for reversible logic circuits, allow any fault that affects no more than a single logic signal to be detectable at the circuit's primary outputs. We show the applicability of our design strategy by demonstrating how the well-known, and very useful, Toffoli gate can be synthesized from parity- preserving gates and apply the results to the design of a binary full-adder circuit, which is a versatile and widely used element in digital arithmetic processing.