Integrated synthesis of linear nearest neighbor Ancilla-free MCT circuits

The rapid advances of quantum technologiesare opening up new challenges, of which, protectingquantum states from errors is a major one. Amongquantum error correction schemes, the surface code isemerging as a natural choice with high-fidelity quantumgates reported for experimental platforms. Surfacecodes also necessitate the quantum gates to be formedwith strict nearest neighbour coupling. State-of-the-artreversible logic synthesis techniques for quantum circuitimplementation do not ensure the logic gates to be formedin a nearest neighbor fashion, and this is handled as a post processingoptimization by the insertion of swap gates. Inthis paper, we propose, for the first time, the inclusionof nearest neighbourhood criteria in a widely used ancilla freereversible logic synthesis method. Experimental resultsshow that this method easily outperforms the earlier two steptechniques in terms of gate count without any runtime overhead.