Int J Theor Phys https://doi.org/10.1007/s10773-018-3806-3 Modular Design of Ultra-Efficient Reversible Full Adder-Subtractor in QCA with Power Dissipation Analysis Firdous Ahmad 1,2 · Suhaib Ahmed 1,3 · Vipan Kakkar 1 · G. Mohiuddin Bhat 4 · Ali Newaz Bahar 5 · Shahjahan Wani 2 Received: 19 March 2018 / Accepted: 15 June 2018 © Springer Science+Business Media, LLC, part of Springer Nature 2018 Abstract Quantum-dot Cellular Automata (QCA) is an emerging nanotechnology and a possible alternative to overcome the limitations of complementary metal oxide semicon- ductor (CMOS) technology. One of the most attractive fields in QCA is the implementation of digital system. As, information loss is a major issue in irreversible digital computation systems. Therefore, reduced heat dissipation is an increasing demand for nano-scale com- putations. Reversible logic designs are good competitor towards sustainable digital systems. This paper presents two new reversible logic gates viz., 3 × 3-New Reversible Gate (3 × 3- NRG), and Modified Feynman Gate (MFG). The proposed gates are tested by designing an optimal reversible single layer full adder-subtractor circuit (RFAS). Based on the simu- lation results, it is observed that the proposed RFAS is an efficient arithmetic logic circuit and has reduced area, less circuit complexity and less number of clock delays over exist- ing designs. In addition, a complete propagation path flow of the RFAS is also presented. Meanwhile, the energy dissipation analysis of the proposed RFAS is verified using three separate energy levels (γ = 0.5E k , γ = 1.0, E k and γ = 1.5E k ), at T = 2 K in QCAPro  Suhaib Ahmed sabatt@outlook.com 1 Department of Electronics and Communication Engineering, Shri Mata Vaishno Devi University, Katra, India 2 Department of Electronics Science, Cluster University, S.P College, Srinagar, India 3 Department of Electronics and Communication Engineering, Baba Ghulam Shah Badshah University, Rajouri, India 4 Institute of Technology, University of Kashmir,Srinagar, India 5 Department of Information and Communication Technology, Mawlana Bhashani Science and Technology University, Santosh, Tangail,Bangladesh