A Method of Mapping and Nearest-Neighbor for IBM QX Architecture

Abstract

In order to solve the problem of mapping a quantum circuit to IBM QX architecture and satisfy connectivity constraints. This paper presents a mapping method, which is divided into two parts: Qubit initial mapping and Nearest-neighbor optimization. To solve the problem of initial mapping of qubits, according to the execution order and interaction of quantum gates in quantum circuit, a qubit mapping order method based on the weight of qubits is proposed. Then, according to the qubit interaction degree in the coupling graph, the initial qubit mapping is completed. In order to solve the nearest-neighbor problem in the mapping process, the quantum cost of non-neighbor two-qubit gate is determined by introducing the lookahead quantum cost method. Our algorithm is evaluated on IBM Q 20. Experimental results show that the proposed algorithm can effectively complete the mapping task even in large-scale benchmark tests. The proposed method is verified by experiments and compared with the existing methods, the optimized results were obtained in 74% of the test circuits.