Nearest neighbor synthesis of CNOT circuits on general quantum architectures

TL;DR

This paper introduces a noise-aware nearest neighbor synthesis algorithm for CNOT circuits on general quantum architectures, improving circuit fidelity by optimizing qubit mapping and gate reduction, especially for architectures without Hamiltonian paths.

Contribution

It proposes a key-qubit priority mapping model and a tabu search-based optimization for CNOT circuit synthesis on diverse quantum architectures, enhancing fidelity and scalability.

Findings

Effective optimization of CNOT circuit fidelity on various platforms

Reduction in CNOT gate count through the proposed method

Extension potential to more general quantum circuits

Abstract

NISQ devices have inherent limitations in terms of connectivity and hardware noise. The synthesis of CNOT circuits considers the physical constraints and transforms quantum algorithms into low-level quantum circuits that can execute on physical chips correctly. In the current trend, quantum chip architectures without Hamiltonian paths are gradually replacing architectures with Hamiltonian paths due to their scalability and low-noise characteristics. To this end, this paper addresses the nearest neighbor synthesis of CNOT circuits in the architectures with and without Hamiltonian paths, aiming to enhance the fidelity of the circuits after execution. Firstly, a key-qubit priority mapping model for general quantum architectures is proposed. Secondly, the initial mapping is further improved by using tabu search to reduce the number of CNOT gates after circuit synthesis and enhance its fidelity. Finally, the noise-aware CNOT circuit nearest neighbor synthesis algorithm for the general architecture is proposed based on the key-qubit priority mapping model. The algorithm is demonstrated on several popular cloud quantum computing platforms and simulators, showing that it effectively optimizes the fidelity of CNOT circuits compared with mainstream methods. Moreover, the method can be extended to more general circuits, thereby improving the overall performance of quantum computing on NISQ devices.