Design for Testability Technique of Reversible Logic Circuits Based on Exclusive Testing

The emerging technology of reversible circuits offers a potential solution to the synthesis of ultra low-power quantum computing systems. A reversible circuit can be envisaged as a cascade of reversible gates only, such as Toffoli gate, which has two components: k control bits and a target bit (k-CNOT), k >= 1. While analyzing testability issues in a reversible circuit, the missing-gate fault model is often used for modeling physical defects in quantum k-CNOT gates. In this paper, we propose a new design for testability technique for quantum reversible circuits in which the gates of a circuit are grouped into different sets and the gates from each set are attached to an additional input line via an extra control. Such arrangement makes it possible to test the gates belonging to a set separately. Our algorithm exploits the feature of many reversible circuits in which the high quantum cost gates have target on the same line and this line is devoid of any control of other gates. All these gates skip addition of extra control for testing. The proposed technique offers less quantum cost in comparison to other DFT techniques published so far.