SnuQS: Scaling Quantum Circuit Simulation using Storage Devices

Since the state-of-the-art quantum computers are still noisy and error-prone, classical simulation of quantum circuits is essential in verifying/calibrating quantum computers and prototyping/debugging complex quantum algorithms. Classical simulation of large quantum systems is challenging due to its exponential increase in space and computation requirements. In this paper, we propose a full-state simulation framework, SnuQS. It exploits storage devices, such as HDDs and NVMe SSDs, to enlarge the available main memory capacity at a small cost. To achieve maximum I/O bandwidth, we propose an overlay-based memory management technique and optimization techniques. We also propose an I/O subsystem architecture that guarantees the maximum bandwidth of each storage device. We evaluate SnuQS on a 64-core CPU and 4-GPU system with 80 2TB HDDs and 10 4TB NVMe SSDs using quantum supremacy and quantum Fourier transform circuits. The experimental result indicates that SnuQS and the proposed I/O subsystem together is an effective and practical solution to scale the full-state simulation of large quantum circuits at about 300x lower cost than the DDR4 DRAM main-memory-only system.