Integrated Synthesis of Linear Nearest Neighbor Ancilla-Free MCT Circuits

The rapid advances of quantum technologies are opening up new challenges, of which, protecting quantum states from errors is a major one. Among quantum error correction schemes, the surface code is emerging as a natural choice with high-fidelity quantum gates reported for experimental platforms. Surface codes also necessitate the quantum gates to be formed with strict nearest neighbour coupling. State-of-the-art-reversible logic synthesis techniques for quantum circuit implementation do not ensure the logic gates to be formed in a nearest neighbor fashion, and this is handled as a post processing optimization by the insertion of swap gates. In this paper, we propose, for the first time, the inclusion of nearest neighbourhood criteria in a widely used ancilla free reversible logic synthesis method. Experimental results show that this method easily outperforms the earlier two step techniques in terms of gate count without any runtime overhead.