Circuit Partitioning and Transmission Cost Optimization in Distributed Quantum Circuits

Given the limitations on the number of qubits in current noisy intermediate-scale quantum (NISQ) devices, the implementation of large-scale quantum algorithms on such devices is challenging, prompting research into distributed quantum computing. This article focuses on the issue of excessive communication complexity in distributed quantum computing based on the quantum circuit model. To reduce the number of quantum state transmissions, i.e., the transmission cost, in distributed quantum circuits, a circuit partitioning method based on the quadratic unconstrained binary optimization (QUBO) model is proposed, coupled with the lookahead method for transmission cost optimization. Initially, the problem of distributed quantum circuit partitioning is transformed into a graph minimum cut problem. The QUBO model, which can be accelerated by quantum annealing algorithms, is introduced to minimize the number of quantum gates between quantum processing units (QPUs) and the transmission cost. Subsequently, the dynamic lookahead strategy for the selection of transmission qubits is proposed to optimize the transmission cost in distributed quantum circuits. Finally, through numerical simulations, the impact of different circuit partitioning indicators on the transmission cost is explored, and the proposed method is evaluated on benchmark circuits. Experimental results demonstrate that the proposed circuit partitioning method has a shorter runtime compared with current circuit partitioning methods. Additionally, the transmission cost optimized by the proposed method is significantly lower than that of current transmission cost optimization methods, achieving noticeable improvements across different numbers of partitions.