QuanPath: achieving one-step communication for distributed quantum circuit simulation

Quantum circuit simulation is an important tool for evaluating designed quantum algorithms. Full-state simulation gives the entire state vectors produced by the running of algorithms. Distributed simulation aims to take advantage of resources on multiple machines (a.k.a. nodes) for high-performance simulation. As a quantum circuit may have many levels, simulation on each level is called a step. The reduction in the cost on each step results in a significant saving in total cost. In existing distributed full-state simulations, the communication cost in each step dominates. In this paper, we propose a new simulation technique, namely QuanPath, which completely eliminates communications and synchronizations on each step until the final merge step. Each node can compute its portion of the state vector independently in parallel. We present detailed mathematical analyses to guarantee the correctness of QuanPath. In the final merge step, an efficient communication scheme is further designed. Experimental results show that when simulating quantum algorithms, QuanPath achieves thousands times of reduction in communication cost and obtains dozens times of simulation acceleration compared with existing techniques. In addition, QuanPath realizes almost linear speedup, so it presents good scalability.