  In recent years, quantum computing has entered the Noisy Intermediate-Scale
Quantum (NISQ). However, NISQ devices have inherent limitations in terms of
connectivity and hardware noise, necessitating the transformation of quantum
logic circuits for correct execution on NISQ chips. The synthesis of CNOT
circuits considering physical constraints can transform quantum algorithms into
low-level quantum circuits, which can be directly executed on physical chips.
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 architecture with and
without Hamiltonian paths, aiming to enhance the fidelity of the circuits after
execution. Firstly, a key-qubit priority mapping model for the general
architecture with and without Hamiltonian paths 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.
Experimental results show that the proposed method can enhance the fidelity of
the CNOT circuit by about 64.7% on a real quantum computing device, achieving a
significant optimization effect. Furthermore, the method can be extended to
other circuits, thereby improving the overall performance of quantum computing
on NISQ devices.
